Sulphur deficiency!

I first started in Hydro and I couldnt figure out my problem. The new growth on my plants kept turning yellow and they were stunted. I was using GH Gro,bloom,Micro. They were experiencing a sulphur deficiency. I didn't know this at the time. I thought it was an N problem.

I have now switched to soil and I'm growing new plants. I have gypsum but it's easy and cheap to get epsom salt. I added 1/4 cup of gypsum to 5 gallon of water during the last feeding 3 days ago. The new growth is yellow but some of them are looking better. What is better to ad to soil, gypsum or epsom salt? Will the leaves recover?

Today my plants are all messed up. They look burnt white. My watering PH is at 6.6 the runoff is at 6.4. I'm starting to think my plants have a disease or virus. I have about 50 plants of several different strains and they are all showing this. They start outfine then turn yellow and then die. The veins are yellow. I can't figure out the problem. The same thing happened in hydro. I went with GH then I switched to Tetraflora. Now Im using soil Happy frog with a little ancient forest. I grow tomatoes with the same stuff and I dont have this problem at all. Ever since I go these clones from this one dispensary I have had this happen. I dont give them nutes and they turn yellow. Whne I give them nutes they simply burn up. I need help.