request for help diagnosing sick sativa seedlings

[GreyMonday]

Hi all. Great forum.

This is my first grow and I'm curious about what might be making my 3-week old sativa girls sick. I'm learning as I go, and the following details probably suggest as much.

Medium: soil, indoors
Brand: Fox Farms Ocean Forest
Strain: Snowcap (straight sativa)
Age: 3 weeks old
Light: LED 144x3w
Distance: 2 ft
Water: 2-3 days, distilled/tap (see below)
Nutes: none yet b/c FFOF
Temps and humidity: 79 degrees; 49% humidity
Pot: 1 gall, transplant to 3 gal soon

These were healthy seedlings for two weeks, in 1 gal pots filled with FFOF and some extra perlite. (No nutes yet because the FFOF is supposedly pretty hot already.) At two weeks I noticed slightly discolored leaves and started to troubleshoot. I learned I had been using a miscalibrated ph meter; the filtered water I was giving them was PH 9.2-9.4. Alarmed, I shifted to distilled water (while I wait for my ph up/down kit to arrive). As the edges of leaves continued to lighten, I decided to flush them after reading around here and elsewhere. The ph of the runnoff (distilled) was 6.5. New leaves in the center of the plant seem healthy; some have started to lighten at the tips; the leaves that were sick before have gotten sicker and curled under. Growth also seems to have slowed. No water since the flush 4 days ago and the soil is not quite dry. Temps in the cabinet are consistently 77-80 degress F.

So, any clear sense of what might be wrong with these little ones? Do I stay the course? Start feeding them?

Many thanks in advance.

 

[Antics]

My first guess from the pictures would be nute burn, but seeing that your PH was being raised by the water, it could easily be lockout at that level. Is this happened to both plants, or just one?

Now I haven't read much about FFO yet, but there might be a chance that the flushing activated nutes in the soil, causing nute burn? (I could be completely wrong about this though)

First step, minimize watering, and keep the PH steady at 6.5. The drastic change from 9.xx down to 6.5 could cause shock easily, and that, or the lockout, could explain the stunted growth, or both.

Keep a close eye on things, if the problem continues onto other leaves, consider transplanting into plain soil to help dilute the nutes, and give the roots new soil to get into.

 

[PeytonManning]

FFOF is too hot for seedlings.

 

[GreyMonday]

Thanks for the advice. I didn't switch the light to the flowering setting when they started turning.

Interestingly, after another week, one plant seems to have resumed growth and the other remains stalled. New leaves look good for several days, then start to lighten and eventually burn. They're going to move to 3 gal pots with a gentler medium today.

Is it possible that 144x3w LED is burning these plants? (I've moved it higher in the cabinet in case; considering the GLR light cycle in case that might help as well.)

Thanks again for any advice.

 

[PeytonManning]

Still looks like a ph problem. But I'm not a soil expert, so I'll wait for them to set the record straight