Lighting Question

[reefy]

I am currently using 2 x 400watts MH for my 90 Gallon reef and I realized that my monti and some of acropora are not in very good condition except my staghorn they are doing great. so my question is, is my light too bright for them?

P.S water parameter is in perfect condition.
PH 8.3 during lights on and 8.15 during lights off.
Calcium:420, Nitrate:5 Dkh:9 Temperature:chilled on 77F.

thanks in advance