ok since no one has answered ill add more to bump it up.. anyways i use ditilled water but just recently i have started using tap water which the ph runs around 7.0 give or take.. it seems to have just happened after i watered them yesterday... i know i didnt over water them because the soil was very dry... so i soaked them with water then filled up the bottoms with some water that had some hydrogen peroxide... thats the only thing i can think of that happened... buts whats weird is all the other plants are fine just one is yellow rest are perfectly green... is it heat stress?? i dont really know anything else i did to make it look burned.. i checked the soil ph and its in the 6.8 field... no nutes ever added and well the soil has so little nutes.. the biggest thing that i dont understand is why its the only one doing it... they have all been grown in the same exact conditions and have been given the same exact thing.. if it were something really wrong with anything i did to it, i would think it would effect all the plants in the same way... hmm im so confused but i guess thats what happens when you grow your first plant :P.. i just wanna figure out why they are dieing so i dont do it again.. or maybe so i can bring them back.. i have searched for these problems and all i can see is it might be a Potassium or magnesium deficiency.. but im not sure.. P.S. if i didnt mention it already they are all bagseed...