What's Going On?

[PharmTox13]

Hey Folks,

So my plants look very happy except various leaves are dried up and brittle, showing browning along the edges. I've posted pics to help with the description. Plants are being grown in an outdoor closet with air from inside the house routed into the closet. I've also got an exhaust fan on the door of the outdoor closet. pH is fine at 6.5 and plants are in FFOF. Temps have hovered around 70-80 over the last week since I started flowering, but prior to that temps got up to 90F but this was uncommon. Veg temps consistently 80-85F. Humidity between 40-55% RH. I've fed them a couple times with FF Big Bloom and Grow Big, but backed off because I saw some of the leaf tips were burnt. Any insight into what is going on? Our water recently switched from groundwater to mostly surface water which is much more soft-could this be a cal-mag deficiency of some sort? Thanks for any help.

 

[GrowingBeard]

I just posted a moment ago about a different issue but I think you are dead on with the call of Cal-Mag deficiency. I started with similar issue to what you have and cleared it right up with CaliMagic. Good luck!

 

[GrowingBeard]

This may help too. It is what I'm using until I can get some advice.

https://www.thcfarmer.com/community/threads/there-is-no-such-thing-as-a-cal-mag-deficiency.62747/

 

[Leew421]

I would move away from cal-mag and get some epsom salt and biomin calcium. The calcium is fully chelated. Most likely you have a lock out. To help this you need lots of RO or distilled. Run about 3 gallons of water and then on the last gallon run calcium and Epsom salt. 3 days later do it again except this time run a low dose of nutrients and add calcium again. The purple stem clear up from a proper dose of Epsom salt. I usually do 1/2 cup epsom to 30 gal water and I'll do 4-5 oz calcium to my res. Of course you can scale it down to your needs. I would do a tsp of Epsom and 2 tsp calcium. Clears up over a week. Check new growth for necrosis or spots

 

[Leew421]

I would also stop using any pH up or down

 

[GrowingBeard]

Excuse the newbie question but is RO or distilled water already at a proper ph? Or why would you stop?

I would also stop using any pH up or down

 

[Leew421]

The soil is the buffer. If you add pH up and down you throw the soil out of whack. Ro or distilled is 7 and very neutral.

 

[PharmTox13]

The soil is the buffer. If you add pH up and down you throw the soil out of whack. Ro or distilled is 7 and very neutral.

While RO/distilled water should have a pH of 7, it has no minerals in the water so therefore it has no buffering capacity. This means adding pH down to RO water will reduce the pH much more than if you were to add pH down to hard water. The minerals in "hard" water act as a buffer. I would agree that the soil acts as a buffer, but I don't see how adjusting the pH of my water will throw off the pH of my soil. I tested the pH of my soil and it was 6.5, the same pH of the water I put in the soil. The only thing I can think of is that salts formed from adding acid (remember your standard neutralization reaction of an acid with a base) and this may inhibit absorption of nutrients at the roots, but this seems rather farfetched. It definitely seems better than the alternative which is to not add any pH adjuster and give the plants highly acidic (pH of ~6) water when adding fertilizer, which would definitely cause nutrient lockout.

 

[Leew421]

The pH up and down stay in the soil causing issues that shouldn't be there. Just cause the water goes in a certain pH doesn't mean it will stay.

 

[KlipschGuy]

That doesn't appear to be ph fluctuation to me. It doesn't look like a common nutrient deficiency or toxicity. That could be to early stages of root rot. I hope I'm wrong!

 

[KlipschGuy]

I'm 29 days bloom today and I don't have nothing like that going on.