Promix HP, GH 3 Parts, LED, Need help with sick plants!

[mulberrysun]

Hi fellow growers! I really need help with my plants since I am totally lost. This is my second grow with the same set up and I am having the same problems as I did with the first grow.

-4x8 tent.
-One Spider Farmer SE7000 650W LED light covering 16 plants in 2 gal pots. SOG method.
-Promix HP w/ 40% perlite.
-Handwatering DTW.
-CO2 currently at 1200 ppm.
-Concealed tent with dehumidifier. Venting fans on/off periodically.
-GH 3 part, CaliMagic, FloraLicious Plus, Big Bud.

Details:
8 Runtz and 8 Ice cream Cake at week 4 of flowering. They started to show purple leaves with yellow/brown spots soon after entering flowering. Symptoms vary, please see the photos. The LED light is running at about 80% and roughly 14" above canopy. Light intensity was measured at about 750 PPFD at canopy. Temperature is 87-90 F when light on, 70 F with light off. The dehumidifier is kind of small and removes the moisture at a very slow rate, so usually the humidity in the tent is at 70%, even higher after watering. For watering, I am doing it every 3 days, so 2 days between water days. I never flush, but have good drain with each watering. I am using well water. Please see my water test result. I mix the nutes in water and ph it to 5.8-6.0. After transition to flowering, I cut off Gro completely for the 3 part and added Big Bud from there. Bid Bug was also at 1/2 recommended and increased to full with the 3 part entering week 4. I am following the GH 10-part feed chart the aggressive version, but used half strength for 1-3 of flowering and just stepped up to full recommended entering week 4. My ppm also increased from ~400 to ~700. My well water is at 110 ppm. Since I am using CO2, during light on, it is only vented about 4 times at 2 minutes each time. When light off, it is vented really well.

Please ignore the lady bugs. They were put in there to fight the mites. The mites are not that terrible yet and I don't think that they influenced my plants a lot yet.

I've done tons of research and reading trying to find out what I did wrong, but I am really lost now and need your help desperately. Nute deficiency? Light burn? Or excess humidity?
All advises are welcomed and appreciated! Thanks in advance!

 

[jguit]

I dont run CO2, so no help there. Why are you cutting your feed in half going into flower? I'm not familiar with 'Big Bud' either. Any reason why you're dropping grow and adding this?

..and you should get your humidity down a bit

My guess is you starved them going into flower.

 

[OrlandoSmooth]

phosphorus and possibly a cal/mag problem. the purple coloring is a tell sign for phosphorus and the rusty colored spots look like Calcium.

You could have two problems- overfeeding and now you have a pH problem and lockout….or you are just under feeding your plants. I would personally flush them and then kick my nutes up, especially cal/mag. It doesn’t look like overfeeding… i don’t see any tip burn.

 

[growsince79]

I don't know how you get away with waiting 3 days to water. My 2 gal promix hp is bone dry after 2 and I don't add perlite. Maybe try every other day at least.

 

[Anthem]

phosphorus and possibly a cal/mag problem. the purple coloring is a tell sign for phosphorus and the rusty colored spots look like Calcium.

You could have two problems- overfeeding and now you have a pH problem and lockout….or you are just under feeding your plants. I would personally flush them and then kick my nutes up, especially cal/mag. It doesn’t look like overfeeding… i don’t see any tip burn.

This appears to be your problem. I am not familiar with cutting out grow from the mix, but if that is the portion of the 3 part that contains "N" not a great idea.
Plants still need "N" in flower. Here is what you need to be looking at

Mulder's Chart

How can you use soil test results? You could ask Mulder. We have learned a lot about plant and soil science in recent decades, but there is a chart that gives us some insight into how the minerals...

www.thedailygarden.us

 

[OrlandoSmooth]

I use the GH 3 part series also. your best bet is to get rid of the big bud and run the 3 part as it was designed. as Anthem stated, cutting out N is a huge problem especially if you do it during the 2 week transition. That being said, I go back to my original post, I don’t think you have a N deficiency because your older fans look pretty green. N is immobile so the plant would start yellowing from the bottom up. However, P deficiencies tend to show that purpling. You shouldn’t be seeing that naturally until late in flower. The rust colored spots are 100% Ca and adding a little bit of calmag shouldn’t put you at risk for burn.

Humidity can also affect how a plant uptakes Ca. I would recommend that you ditch the CO2 (I don’t think you run enough light for it to matter) and opt for a 24 hour exhaust fan with a scrubber that has enough power to create negative air pressure in your grow space.

 

[mulberrysun]

I dont run CO2, so no help there. Why are you cutting your feed in half going into flower? I'm not familiar with 'Big Bud' either. Any reason why you're dropping grow and adding this?

..and you should get your humidity down a bit

My guess is you starved them going into flower.

I was always feeding less than GH recommends, from 1/2 of "light feed" to 1/2 of "aggressive feed" until now. Running full Aggressive feed now. I was hesitate to give too much nutes because I burnt my last grow, but those were autos. I deleted grow coz I followed a friend's advice. Looks like it is the wrong thing to do. I basically used Big Bud to replace the GH KoolBloom. I agree that I probably starved my plants, and the added CO2 might just made it worse. Not sure if I set up my light right though. The plants are pretty close to the light bars and I don't want to stress them by too strong of light.

 

[mulberrysun]

I don't know how you get away with waiting 3 days to water. My 2 gal promix hp is bone dry after 2 and I don't add perlite. Maybe try every other day at least.

I actually really want to water them more frequently, but this shit doesn't dry out! It was the same with my last grow in 2 gal pots also. I've read about similar experiences from others using Promix. Drying time improved though this time coz I added perlite. So if you're feeding every other day, may I know your ppm? I heard that Promix doesn't like heavy feeds?

 

[mulberrysun]

This appears to be your problem. I am not familiar with cutting out grow from the mix, but if that is the portion of the 3 part that contains "N" not a great idea.
Plants still need "N" in flower. Here is what you need to be looking at

Mulder's Chart

How can you use soil test results? You could ask Mulder. We have learned a lot about plant and soil science in recent decades, but there is a chart that gives us some insight into how the minerals...

www.thedailygarden.us

I'll try to resume the grow and follow the official feed charts and see from there. Thanks!

 

[Anthem]

I use the GH 3 part series also. your best bet is to get rid of the big bud and run the 3 part as it was designed. as Anthem stated, cutting out N is a huge problem especially if you do it during the 2 week transition. That being said, I go back to my original post, I don’t think you have a N deficiency because your older fans look pretty green. N is immobile so the plant would start yellowing from the bottom up. However, P deficiencies tend to show that purpling. You shouldn’t be seeing that naturally until late in flower. The rust colored spots are 100% Ca and adding a little bit of calmag shouldn’t put you at risk for burn.

Humidity can also affect how a plant uptakes Ca. I would recommend that you ditch the CO2 (I don’t think you run enough light for it to matter) and opt for a 24 hour exhaust fan with a scrubber that has enough power to create negative air pressure in your grow space.

So you are saying "N" is immobile
That goes against everything I have Learned

 

[OrlandoSmooth]

So you are saying "N" is immobile
That goes against everything I have Learned

mistyped. meant mobile. hints why it will yellow at the bottom first to transfer nutes to the new growth

 

[jguit]

I actually really want to water them more frequently, but this shit doesn't dry out! It was the same with my last grow in 2 gal pots also. I've read about similar experiences from others using Promix. Drying time improved though this time coz I added perlite. So if you're feeding every other day, may I know your ppm? I heard that Promix doesn't like heavy feeds?

Lowering your humidity would most likely help with the frequency of your feeds. 2-3 days is typically how often i feed plants in Promix @ approx 80F / 50 RH. It's not so much that ProMix doesnt like heavy feeds but it doesnt like to dry out, especially in flower. That's when it gets a bit salty. I usually feed anywhere from 1.5 - 2 EC, depending on stage, strain, etc..

 

[growsince79]

Lowering your humidity would most likely help with the frequency of your feeds. 2-3 days is typically how often i feed plants in Promix @ approx 80F / 50 RH. It's not so much that ProMix doesnt like heavy feeds but it doesnt like to dry out, especially in flower. That's when it gets a bit salty. I usually feed anywhere from 1.5 - 2 EC, depending on stage, strain, etc..

Agree. Op has uptake issues due to high rh. Lowering the humidity will help. Promix hp drys out very fast especially in mid flower. Add 40% perlite and idk how it holds much at all. If I added 40% to 2 gal pots, I would have to water small plants twice a day.