Noobs first grow and need help with my seedlings

burnoutstoner · Mar 13, 2026

Hey everyone, this is my very first cannabis grow and I’m already feeling a bit lost with my 4 seedlings (regular seeds). They’re 12 days from sprout and I’m trying to figure out if I’m dealing with salt buildup, overwatering recovery, light stress aftermath, Ca deficiency, or just normal seedling weirdness. Any help or eyes on this would be hugely appreciated.

Setup & Gear

Tent: Small 2x2 mother/seedling tent (getting warm ~84°F with light on, but I’ve got AC Infinity Cloudline T4 exhaust + oscillating fan) I also moved the led driver to the outside of the tent.
Light: Mars Hydro TS 1000 (was too close ~5 days ago, now at 30 inches above canopy, 24/0 schedule)
Medium: Fox Farm Pre-buffered 70/30 coco coir (I also pre buffered myself) in 16 oz red Solo cups, 5 drain holes each, elevated on a rack for full drainage
Water: RO (~10–47 µS EC baseline)
Nutes: Jacks 321 (5-12-26 + Calcium Nitrate 15-0-0 + Epsom Salt)
Additives: GH Rapid Start (1–2 ml/gal), GH Armor Si (1–2 ml/gal), GH CaliMagic (0.5–1 ml/gal recently), Great White mycorrhizae (¼ tsp/gal)
pH: Targeting 5.8–6.0 (mix starts there but creeps to 6.2 after a few days in storage)
EC: Started very low (~505 µS)
Environment: 72–84°F RH: 70-82% VPD: 0.7-0.8 kPA
Mr. Nice seeds regular photoperiod: Critical mass seeds

Timeline & What I’ve Done

Days 1–7: Very light spray bottle watering (20–60 ml targeted around stem every day), kept evenly moist, EC ~500–550 µS, pH 5.8
Around day 7–10: Noticed slight yellowing + brown tips/edges on fan leaves, some drooping, very compact nodes (almost no spacing), slow upward growth
Day ~8: Suspected my light was way too close roasting my seedlings → raised to 30 inches (fixed that)
Day 8: Stopped all watering/feeding for 3 days to dry out coco (cups felt heavy before, and suspect over watering because green algae was forming on top, so I covered the algae with a small amount of coco to kill it)

Today (day 12) Flushed with 200 ml (740 EC Jacks 3-2-1 mix+ Cal-Mag 1 ml/gal + Silica + Rapid Start+mycorrhizae)
and then tested the run off

Current Runoff Readings

Cup 1: 1300 µS / 5.6 pH
Cup 2: 1025 µS / 5.9 pH
Cup 3: 1170 µS / 5.8 pH
Cup 4: 1410 µS / 5.5 pH
(Drift +275 to +660 over input – clear salt buildup)
Today (day 12) After testing the runoff and seeing the high EC readings I continued to do a very excessive flush, I flushed each cup with 1 liter of 740 EC / pH 5.9 Jacks mix (740 EC Jacks 3-2-1 mix+ Cal-Mag 1 ml/gal + Silica + Rapid Start+mycorrhizae). Let it fully drain out the bottom holes.

Current Plant Status

New top growth still looks healthy/green (no new yellowing there)
Lower fan leaves have yellowing + brown tips/spots/edges (old damage from light stress + possible Ca issue?)
Some leaves still mildly droopy (improving after dry-out?)
Nodes extremely compact (almost no internode spacing)
Growth feels very slow/stunted above ground (but roots might be catching up?)

Questions / What I Need Help With

Did the 1 liter flush at 740 EC do enough to clear the salts, or should I do another flush with lower EC (400–500) or plain pH’d RO?
How soon can I feed again after this big flush? When top is dry? What EC should I start back at?
Is the compact nodes + slow vertical growth normal at day 12 in coco solos, or is it stunting?
Brown/yellow tips – is this just light burn scars, or ongoing Ca/Mg lockout? Keep Cal-Mag in every feed?
Anything else I’m missing? (Ventilation is decent with T4 + fan, RH 70–82%, temps 72–84°F day)

I’m trying to be patient and document with photos every few days, but as a first-timer it’s hard to tell if they’re just slow or actually in trouble. Any advice, similar experiences, or “wait X days and they’ll explode” stories would help calm my nerves.

Thanks in advance

Gmix · Mar 13, 2026

Day 8: Stopped all watering/feeding for 3 days to dry out coco (cups felt heavy before, and suspect over watering because green algae was forming on top, so I covered the algae with a small amount of coco to kill it)

Don’t let coir dry out withholding the water for 3 days was your biggest mistake. Even with the green algae ( I can’t fully rem but i have read it forming on coir before & it not being a serious concern)
I don’t grow in coir no more so a coir grower will have more information for you.

I did skim a bit as I know you would be in better hands with someone who’s more knowledgeable on it ( that said I really mean the pros that hang around here )

You can’t really overwater coir
It needs watering daily and as they grow so does the need to water more than once a day.
unlike soil as said you can’t really overwater coir

Gmix · Mar 13, 2026

Coir also has nothing the plant can feed on as it inert & they do if you haven’t fed them someone who knows more about jacks/coir should help you out with your feeding schedule

burnoutstoner · Mar 13, 2026

Gmix said:
Day 8: Stopped all watering/feeding for 3 days to dry out coco (cups felt heavy before, and suspect over watering because green algae was forming on top, so I covered the algae with a small amount of coco to kill it)

Don’t let coir dry out withholding the water for 3 days was your biggest mistake. Even with the green algae ( I can’t fully rem but i have read it forming on coir before & it not being a serious concern)
I don’t grow in coir no more so a coir grower will have more information for you.

I did skim a bit as I know you would be in better hands with someone who’s more knowledgeable on it ( that said I really mean the pros that hang around here )

You can’t really overwater coir
It needs watering daily and as they grow so does the need to water more than once a day.
unlike soil as said you can’t really overwater coir

Thanks a lot for taking the time to reply — I really appreciate it, especially since it's my first grow and I'm still trying to wrap my head around coco.You're right — I think the 3-day dry-out was probably the biggest misstep. I was trying to correct what felt like over-wetness/drooping, but I clearly went too far the other way. Lesson learned: coco really does want to stay consistently moist (not soggy, but never bone-dry either).The green algae on top was light (mostly on the perlite bits), and I already covered the surface with a small amount of fresh coco after the flush, so it's dying off now.

Good to hear it's not usually a big deal. Since I just ran 1 L of ~740 EC mix through each 16 oz cup (with good drainage — 5 holes + elevated rack), the medium is pretty saturated again. I plan to let the top dry out a bit (maybe 1–2 days max this time) before the next light watering. For someone who's not growing in coco anymore, do you remember roughly how often you were watering in early seedling stage (days 10–21) to keep it from drying out too much? Thanks again — I'm definitely listening to the coco pros here. Hoping to see some upward stretch and new nodes in the next week now that the salts are (hopefully) flushed.

cannafarmer420 · Mar 13, 2026

burnoutstoner said:
Thanks a lot for taking the time to reply — I really appreciate it, especially since it's my first grow and I'm still trying to wrap my head around coco.You're right — I think the 3-day dry-out was probably the biggest misstep. I was trying to correct what felt like over-wetness/drooping, but I clearly went too far the other way. Lesson learned: coco really does want to stay consistently moist (not soggy, but never bone-dry either).The green algae on top was light (mostly on the perlite bits), and I already covered the surface with a small amount of fresh coco after the flush, so it's dying off now.

Good to hear it's not usually a big deal. Since I just ran 1 L of ~740 EC mix through each 16 oz cup (with good drainage — 5 holes + elevated rack), the medium is pretty saturated again. I plan to let the top dry out a bit (maybe 1–2 days max this time) before the next light watering. For someone who's not growing in coco anymore, do you remember roughly how often you were watering in early seedling stage (days 10–21) to keep it from drying out too much? Thanks again — I'm definitely listening to the coco pros here. Hoping to see some upward stretch and new nodes in the next week now that the salts are (hopefully) flushed.

I dont do coco but I see you are already in good hands. Happy growing

burnoutstoner · Mar 13, 2026

cannafarmer420 said:
I dont do coco but I see you are already in good hands. Happy growing

Thanks! Hoping some of the coco growers here can help me save them before they die. They don't look to healthy right now, but maybe its just old damage from the light stress and I need to wait .... I am not really sure.

WinJr63 · Mar 13, 2026

I grow in organic coco coir from the bricks which are loaded with nutes (npk 1:1:1 , ph 7.0)

I do not like solo cups, I had major issues.

My friend transplant those ladies in final pot, they will recover .

My 5 plants where in way more bad shape then yours.

I don't buffer my coco coir someone else should be able to help u on that.

Keep us posted with grow.

burnoutstoner · Mar 13, 2026

WinJr63 said:
I grow in organic coco coir from the bricks which are loaded with nutes (npk 1:1:1 , ph 7.0)

I do not like solo cups, I had major issues.

My friend transplant those ladies in final pot, they will recover .

My 5 plants where in way more bad shape then yours.

I don't buffer my coco coir someone else should be able to help u on that.

Keep us posted with grow.

Thanks for the input, I appreciate it. This is my first grow so I'm definitely learning as I go.

Interesting about the organic coco bricks already having nutrients in them — I didn’t realize some came pre-charged like that. Mine is plain coco so I’ve been trying to manage the nutrients myself with Jack’s 3-2-1.

Good to hear your plants bounced back even when they were worse off than mine. That definitely gives me some hope. I’m planning to transplant into the final pots soon, so hopefully that helps them take off.

I’ll keep the thread updated as things progress. Thanks again for the encouragement.

WinJr63 · Mar 13, 2026

burnoutstoner said:
Thanks for the input, I appreciate it. This is my first grow so I'm definitely learning as I go.

Interesting about the organic coco bricks already having nutrients in them — I didn’t realize some came pre-charged like that. Mine is plain coco so I’ve been trying to manage the nutrients myself with Jack’s 3-2-1.

Good to hear your plants bounced back even when they were worse off than mine. That definitely gives me some hope. I’m planning to transplant into the final pots soon, so hopefully that helps them take off.

I’ll keep the thread updated as things progress. Thanks again for the encouragement.

You bet man, Amazon has those coco bricks.

WinJr63 · Mar 13, 2026

Oops. Scratch that organic coco coir.

It is called: Wonder Soil BrickPlus.

opt1c · Mar 14, 2026

As other have mentioned you can’t overwater coco. The key caveat in that equation is drainage though. With those solo cups you are probably not getting it. If you move them into larger pots made for plants you’ll probably have better results. Another nice thing about coco is it will naturally wick up as much liquid as it needs. You can toss the pots in a tray with an inch of your mixed nutrients and let them sit for a good 10 mins and then move them to a rack to drain. Helps a ton if the coco got a bit too try. It can become hyrophobic and get dry pockets where roots won’t grow and liquid rolls off of. Soaking them will get these areas saturated again. You might also want to look into adding some BTi like gnatrol or similar in small amounts to your feed. Gnats can do a number on seedlings in coco if they show up.

burnoutstoner · Mar 14, 2026

opt1c said:
As other have mentioned you can’t overwater coco. The key caveat in that equation is drainage though. With those solo cups you are probably not getting it. If you move them into larger pots made for plants you’ll probably have better results. Another nice thing about coco is it will naturally wick up as much liquid as it needs. You can toss the pots in a tray with an inch of your mixed nutrients and let them sit for a good 10 mins and then move them to a rack to drain. Helps a ton if the coco got a bit too try. It can become hyrophobic and get dry pockets where roots won’t grow and liquid rolls off of. Soaking them will get these areas saturated again. You might also want to look into adding some BTi like gnatrol or similar in small amounts to your feed. Gnats can do a number on seedlings in coco if they show up.

Thanks for the advice! I actually already have Summit Mosquito Bits on hand, which I think contain the same BTi (Bacillus thuringiensis israelensis) you mentioned like in Gnatrol. I haven’t seen any gnats yet, but I can start soaking the bits and adding the water to my feed as a preventative just in case. Appreciate the tip

opt1c · Mar 14, 2026

I would crush them up and then add just a bit to each batch you mix up and let it sit for an hour or prior to watering. Last thing you want to do is add stagnant room temp water to your ph’d nutrient mix. Depending where you are you might find small amounts of gnatrol on auction or craft seller sites at reasonable prices. It dissolves instantly and the thing I find I have the least of these days is time, so it’s worth it for me. Happy growing!

burnoutstoner · Mar 14, 2026

opt1c said:
I would crush them up and then add just a bit to each batch you mix up and let it sit for an hour or prior to watering. Last thing you want to do is add stagnant room temp water to your ph’d nutrient mix. Depending where you are you might find small amounts of gnatrol on auction or craft seller sites at reasonable prices. It dissolves instantly and the thing I find I have the least of these days is time, so it’s worth it for me. Happy growing!

I have just added 4 table spoons of Summit Mosquito Bits to 1 gallon of RO water. On my next feeding I will filter the bits out and use this water to mix my Jacks 3-2-1 nutes? How often do I need to use these Mosquito Bits?

Noobs first grow and need help with my seedlings

Noobs first grow and need help with my seedlings

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