I think it may be from nutrient lock-up from PH fluctuation. I'll give them another day to see.
Hey Mongobud,
I'm not the best plant problem diagnoser in the world, but I agree that you may have a nute lockout issue, possibly Mg. And you're probably right that ph fluxuation may be the problem, especially if the ph was below 5.0 for an extended period of time.
But you may have a water problem as well, in my opinion. It looks like your leaves are drooping a bit (like your plants are being overwatered) which in my experience means the roots aren't happy; they might not be getting enough oxygen and/or not taking in the nutrients.
Here's a little checklist to run through to make sure you problem isn't caused by water problems:
1. High water temperature (above 75* F). High water temps means lower dissolved oxygen levels and less nutrient uptake, but that doesn't seem to be the case in your instance.
2. Water level too high. Are the roots in the water? If so, is the water level 2" or more below the pots? It's useful to have some of the roots above water level to help with oxygen uptake.
3. Tap water or water from a water softener. Are you using tap water? If so, do you know what the ppm of the water is? High tap water ppm usually means high levels of calcium, and high levels of calcium can lock out Mg. And you say you are having a hard time stabilizing the ph; calcium acts as a buffer (buffers the water so it stays at 7.0, for instance) and if there's lots of calcium in the water it will take a lot of ph down to eventually counteract it and stabilize the water at a lower ph.
4. Chlorinated water. If you are using tap water and you don't let it sit for 24 hours or so, you might have high levels of chlorine and ammonium, which can also lock out Mg.
5. Chasing ph. Making rapid and large changes in the ph can shock the plants, giving them an overall droopy appearance. In my opinion, it's better to let the ph be excessively high/low and adjust gradually then to adjust all at once to get it back in range.
6. Air pump not adequately oxygenating the water. What size pump are you using, are your airstones clogged, etc.
7. The dreaded pathogen. How do your roots look? Any slime on the roots? Any smells in the reservoir?
Anyways, take this for what it's worth...and good luck!