cant figure it out...

posting for a friend... i'll make it short and sweet...

Problem: leaves started going a grayish color and very brital from the tip towards the stem then started going yellow in spots

More Detail: The plants have 2 cfl lights at 18/6 and are in red cups with potting soil that was found in a plant outside. The lights arent on timers and when he went away for a while the plants got 4 days of 24hour light. When he got back the plants showed alittle discoloration but not much. Slowly the leaves kept getting more brital with the gray color. he added a bit of shrub fertilizer and the problem stopped but some spots then went yellow. he cut off any damaged leaves and is now planning on transplanting them into cups that have freshly bought top soil. Should this help the problem? im thinking what happened was since the soil was already used from the plant outside nutrients may have been low and then when he tried fixing that seeing as though they are so young (2 weeks) they got fert burn.

btw overwatering isnt possible cause he uses the wick system. just tap water that was left to sit to let the bad stuff get out of it.

Need a pic..Tell him to use potting soil( a good one) not top soil. add 30% perlite and tbsp dolomite per gallon. Get some pots too.

Welcome

he just picked up potting soil today i think and was planning on switching out the soil. he is only going with the cups until he turns them over to 12/12 (he is growing the mto 6" then switching them, he is trying a sog grow i think) and then he is moving them to something bigger. with fresh potting soil should the plants last without nutrients until they are 6" or so? he doesnt know when to start fertilizing them, what to use, or how much to use. thanks for the help btw seeing as though this is my first post

Good potting soil is good on nutes for 3-4 weeks. Not meaning reg MG. If he picked MG make it the organic line.

so i gues lets just say its ok potting soil and say it lasts 2 weeks. by then the plants should be 6" and then they should be switched into the bigger pots and put on 12/12. Once he starts 12/12 should he also start fertilizing? fertilizer wise can you just get any miracle grow fertilizer or is there a special brand or something? and they should have directions for use correct?