i have two plants growing right now, both 6 weeks old, and growing very nicely. but recently, one showed signs of problems. the lower leaves showed very bad yellowing, which was immediately followed by dark brown spots. my girlfriend, who knows a lot about plants in general, said that it looked like a nitrogen deficiency, and a book i had said the spots could be potassium deficiency. that would make sense, as they are currently in a very phosphorous-rich soil. i treated them with a high nitrogen/potassium fertilizer, and the condition seems to have halted. nevertheless, i want to check with more experienced growers to make sure i had the correct diagnosis and correct treatment. my only real worry is if the spots are a disease or something of the sort. the plants are still growing nicely, one 7" tall and the other 6.5", with lots of lush leaves about. still, the fear of the problem returning hangs over me, and i need to know what went wrong, and what to do in case it happens again. thanks
If the problem went away when you fertilized it, it was an N deficiency. With your phosphorus rich soil, I would have guessed over-fert because seedlings don't need any fertilizer for the first 3.5 weeks of life.