A little seedling advice?

Cletus clem said:

You can give a plant too much light without heat being the issue. It will present as bleaching. Herming can be a sign of too much light as well. Hid lights will cause heat stress along with it because of the infrared light. Leds are more likely to cause light stress/damage without heat being a factor.

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Ya never had an issue with my HID but I've only used them a few times for veg and went back to T5's, seem to work just as well. I have seen and heard about some major bleaching with LED though. So how much is to much I wonder? I use 2 600's 1-MH and 1-HPS, for a appr. 4x4 and a 1000 some times. Perhaps the MH would be worse as it has UV.