Can anyone tell me why this happens

hello I have a quick question. so ever since I set up my high pressure sodium light my plants have exploded under it they have never looked so healthy BUT sometimes they start dropping really really bad but then hours later or the next day they are back to normal is this something I should be worried about. what's going on with them.
thanks for all your help.

usually if my plants look like that its time to water or maybe its to hot. whats the temps like in there?

My plants took a while to get used to hps from cfl the soil drys up a lot faster

either underwatering or plants are just exhausted from all the new work theyre doing. if they always perk up in the morning then thats all it is. they will get used to this if that is the case. aloha

yes the soil does dry up very quickly in there. and to answer the temp question I'm unsure of the temp cause my thermometer broke but I have a small air purifier aiming rite st them is that a good idea or no. also what kind of plants grow low and bushy and I have another unidentified plant that's tall and growing out. also i have two plants growing under the same light and they keep growing towards the light is this bad or what should I do.
thankyou

yes the soil does dry up very quickly in there. and to answer the temp question I'm unsure of the temp cause my thermometer broke but I have a small air purifier aiming rite st them is that a good idea or no. also what kind of plants grow low and bushy and I have another unidentified plant that's tall and growing out. also i have two plants growing under the same light and they keep growing towards the light is this bad or what should I do.
thankyou

growing to the lights are normal. just rotate your plants from time to time to assure uniform light coverage. also if u want short bushy plants, just top over and over. aloha

Dude i live in vegas and here, it's fucking hot in the summer. When I do grow outside, I see this from time to time. Your plants are too hot, or they are thirsty. HPS's put out more heat than a CFL so your gonna have to water more often. The good news is your plants will probably grow faster, but your gonna have to work a little more.
Buy a fucking thermometer man, you can get one from the 99 cents store, you pin it up in your growroom, bam. You say you have an air purifier, idk if thats a oscillating fan but you might have circulation problems too. If you find out you have a heat problem it could as simple as fixing the fan/exhaust system, or as serious as having to switch back to CFL, LED, or a the T5 type fluorescents or adding a small air conditioner. Good luck!

More water.