light problem? ??

alright doing a new thread seeing no one jumped on old on.
I have several plants sitting under my 400hps light with 2ft in between,I gave a complete setup with 175cfm exhaust fan with portable ac ,going light on the advance nutrients, ph perfect solution. Temps stay between 69-76.
Here's the deal, plants are vibrantly healthy only sign of something is up is the droopyNess of the leaves .I water when pot is light so it's nit a watering factor nor nutrient toxicity or deficiency.
If I move light any closer the leaves sagg but it's 73 degrees with circulation and obviously when I keep the light 2ft or more away the plant perks up ,nit sure why last grow I had a 600hps sitting 8inches off the top and they loved it so yea
 
That what I thought and I got curious and checked the pots sides and they were fairly warm So I have the ac routed to put some cool air on em and far as I can tell it's light sensitivity which is strange
 
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