The MH are indeed probably at fault. You have a 96W MH bulb over a 10 gal tank which mostly likely has some sand and rock. Lets say you have 2 gal of displacement, leaving 8 gal of water. This equals 12W light/ gallon of water (96W/8gal). LPS corals like 5-7 W/gal and they need max. light. Zoos need much less light and do well under T5's or bright fluorescents. Hopefully, the remaining three colonies will adjust. Move them to the lowest spot in the tank and move them up (?) slowly as they acclimate.