My plants seem unhappy after i put them under the HPS?

I pregrow my plants in a small box with a couple of mixed T5's
Always had super healthy, happy plants under them. as soon as they outgrow the small box i transplant them into their final size container and they go under a 250w hps (about 50cm distance from canopy)
and EVERY GOD DAMN TIME they change from deep green happy plants with their leaves all upright, to just not so deep green, slightly drooping plants. Also the surface of the leaves seem to get a little wrinkly, not as smooth as before.
Anyone knows what the cause of this could be?
i'm thinking maybe transplant shock + too big light diffrence?

ensure they are in a minimum of 3usg

avoid overwatering

hang 2 temp gauges low and high

avoid overwatering

ensure you have a small fan to remove 02 and heat

and yeah avoid overwatering

good luck

3usg?

overwatering is nearly impossible, i'm using canna terra mixed with about 30-40% perlite
Got electronic temperature monitoring top & bottom , wich are recording the same, 26-27 celsius
i've got a nice oscilating fan mixing up all the air.
also got an exhaust fan that activates whenever the temperature goes above 27celsius

Its light stress. They are getting sunburnt. Harden them over a weeks time. An hour the first day or two then 2 or 3 then 4 or 5 and so on. Give them time to build up a defense against the uv.
Or raise the light a few feet and lower it a bit every day

Yup.harden them off first as HPS puts off alot of IR.

i hang mine to the top of the tent that gradually bring them down as they get used to it

I shave my head, and whenever I end up under my hps it feels like my head is getting sunburnt. They are powerful lights, easy them into it.

If you transplant then immediately put them under hps and they wilt and get wrinkly... Removing them from cooler softer lighting to a harsh H.P.S is probably an issue especially after repotting as this is asking a lot of the plant. Recover from transplant, adapt to new lighting ect. It needs to get comfy and re-establish its roots ect before you demand them to pull up the water it takes to keep the leaves "erect and pointing north" and not crinkle up and get leathery.

Thanks alot for everyone who replied!
I'll give her some time to adjust to the HPS, thanks alot again!