You are right Valerie I have a Potassium deficiency I am currently addressing.
At first I thought it was heat/light stress, then realized I was wrong, because it is only effecting one plant. The
@ViparSpectra KS5000 puts out a lot of light, but testing it along the way help me to eliminate any chance of heat or light stress.
Potassium deficiency can often look like heat or light stress and the symptoms are almost identical. So today I gave them all a boost of (K) and should see result in a couple of days.