You might try pulling your light back just a touch for a few days until they get used to the new lighting.......hps is a big step above your original lighting....I have some new seedlings I just stuck in my hydro and can't use my light on them yet....mh1kw.....even from about 4 feet....have to edge it in bits at a time or they get heat stressed even though room temp is good. . Are they perked up in the morning? Maybe I'm just being paranoid.