Ive got the same problem with my 2 plants in veg right now only mines not hydro and i got them under a 125 watt plant light. the leaves have been dieing out each time a new layer or the leaves start to grow above. all the ones die out below so now i have a 12 inch stem with a set of 2 leaves and 2 more appearing but the rott has already started on the ones on top? any suggestions?