I had a brown dino problem for a long time and then lowered my temps from low mid 80s to 70s F and it's gone and has not come back for months. I had tried everything.
Try using plastic chrome aquarium backing. It's the same as the picture backing except it's chrome. I've had it next to my 175MHs for 2 years no problems.
When does know its time to replace metal halide lamps. Wait till they burn out or what? Mine are about a year and a half old.I do have a slime algae problem.
Thanks.