I'm no expert but a friend who is gave me some advice saying that if leaves start curling up instead of down before they burn then it's heat damage.
But I'm sure you'll get a more expert answer in a few mins
11 hours under CFL's/Fluro's, 5 hours under 250watt HPS, temps have been a bit high at times, but they're also slow growers so I'm thinking I could have given then too much nutes for their size rather than age. Both options are as viable as each other.
In my experience a general overall yellowing of a leaf is from lack of food or light.
I've been fooled before with small plants, thinking I was getting nutrient burn at the tips of the plant. Then I slacked off on food and it got even worse. I was actually underfeeding.
what temps do you reach in there.. i would definitely go with nute burn, just for the fact cfl's and a 250 watter shouldn't make enough heat to cause damage.. unless the 250 watter is right on the plant. i have seen temps in the 90's w/o damaging the plant.. to me it really looks like nute burn.. could be over watering too...
Doesn't really look conclusively like either, and you'd be hard pressed to burn your plants with that lighting setup unless they're WAY too close. I'm leaning towards a nutrient problem.