First time setup-problem w/ leaves yellowing

[Miadunn]

Hey board!

Here is my new setup that I got for Christmas. It's 20x20x30 with a bank of 4 ho t5 lights. There is one fan in the corner and the front has sliding doors. The temp is about 75 all day with the lights on for 12hrs. I think the lowest it's gotten is 60 at night. I have just been putting water in the bottom to keep up humidity and spraying them in the morning. Humidity runs btw 25% up to 75%

Right now, i just have two orchids you see in there. The main one has been sprouting new roots before i put it in the box. i had previously repotted when I first brought it home and all the roots had died so i was excited to see this new growth. So that being said the leaves were just in ok condition. Recently, I have lost 2 bottom leaves due to them yellowing and dropping off. I know this is sometimes normal but I see another leaf starting to turn so I'm worried. I turned my light so that only two bulbs are on and moved the pots all the way down in the space thinking the change of no light to the grow box was a bit too much.

Do you have any advice on what to change?