Twisted, discolored leaves (new growth)

My plants were doing fine and suddenly these two (out of 20 plants) are showing these weird symptoms. They look discolored and new growth looks deformed and twisted. Temperatures are fine (using 315W CMH) never exceeding 30C, at about 35CM distance, water PH 5.8-6.8, I have a big fan pointing at them (this might be the reason but as I said it's only happening with these two), bio bizz soil that I reused many times and I suspect it might be the culprit, watering when pot feels light.

Notice the twisted yellowing leave on the first pic, right side of the photo.

Any ideas?