Thanks for the clarification.
1). The the photo you said was worse was taken when the leaves were going bad. The first two posted are actually newer. I'll post a new photo taken tonight.
Root exposure starts at 1/2 inch when tanks are full. Then increases as the plants draw. I change water every 14 days. No mildew and the water smells normal.
Yes the kinetico softener takes salt. But it's not in the water.
The
growing medium is Rock wool.
One air stone per tank bubbling strongly. Placed in the middle.
There are no bugs, no powdery stuff.
In don't know the air temp under the light, I'm not equipped to check it directly.
I just changed the tanks again. I will check it periodically for pH.
Two things have changed since the brown tips. 1) changed the tanks and 2) I raised the light up 9 inches.