My seedlings have been growning for about 2 weeks now and out of nowhere they started showing brown spots on the leaves and tips, i dont see any signs of pests and i just started using the bottles recommended dose of nutrients so i dont think its nute deficiency, could it be nute burn? I'm using liquid karma, cal mag, and PBP grow all mixed with distilled water and PH measures to about 5.5-6.5. I need suggestions on what to do. I included pictures. Please Help.