I have no Idea thats very strange I didnt know it was Organic soil. But if your heat is under control, Ph of water and soil is fine, There is decent drainage and your water is not just straight tap then it has to be that soil. Maybe the clear pots and light burn on the roots I would use a red solo next time but it just has to be the soil isnt aerated or its just got too much or too less nutes.I have never had this problem at such a young age, Hope it works out dude.
-My heat does get pretty high, up to 82-86 at peak times. So i just powered down the lights from 165 to 110.
-My water IS straight from the tap, the ph and ppm readings are tap water. Should I try buying some distilled water >?
- I duct taped the cups so the light wouldnt go through.