Looks like over watering symptoms but runoff pH and PPM measurements may tell us a different story.
I did a light feeding like the other guy suggested. PH was the same on run off as what I put in. 6.4PH.
PPM's on average for all six plants was around 1000ppm
Ok those numbers are fine. Has the problem appeared to have stopped in the past 5-7 days? Like I mentioned in my past post, it look like over-watering. Although, the new growth looks fine. This makes me think it was over-watered for awhile at one point but is recovering. The damaged leaves will not recover.
Yesterday was the worst day. I noticed it because I was going to check the soil and water them. It had been a week since the last watering. I always check with a probe. That way I can check all the way to the bottom of the pot for moisture level.
Watering and feeding are my achilles thus far. I must over water and I always under feed. I'm always nervous about over feeding.