Thanks for taking time to read this. I have grown several times before but always from cuttings in the past, this is my first time from seed so I am not used to caring for plants this young. I have 5 white widow seedlings grown from seed which, while waiting for me to build a grow room, spent 2 weeks on a window sill. This caused them to stretch, but 3 days ago I transferred them to the grow room (in my garden shed) and I assume this problem will sort itself out. All 5 are growing under a 400w Philips Son-T Agro lamp throwing out 55,000 lumens. The top leaves are approx 50cm from the bulb and it does not seem too hot when I put my hand there (although I have not got an accurate temperature reading yet). The light is on 18/6 at the moment. The grow room has an extractor fan and also a stand alone fan for circulation. I water every 2-3 days (in the pics, I have just watered) and the last time I watered I added a little 1/2 strength Ionic soil grow nutrient solution. The problem is that one of the young plants this morning when I checked has very dry crispy leaves which crumble when touched. It's environment is exactly the same as the others, all of which seem to be healthy. The first pic shows the problem plant from above, the second shows it next to one of the healthy seelings. Does anyone have any ideas why this is happening to just one plant and what action I should take. Could it be heat related, watering or nutrients? This plant seemed to be the strongest of all of them until today and I was hoping to use it as a mother to clone from when it was older.