Do you test your water?? If so what are you calcium and ALK at??? and Mag if you test for it. Also the ph and specific gravity? you may need to move the brain up a little higher for more light.
Cool. You can get away with a few small fish in that 20H. Add that clown and maybe like a blenny or something. Maybe a few inverts, like cleaner shrimp.
Your tank looks good, the coral in your first pic is actually a Trachy or as you called it an open brain. It is not doing very well judging by the pic's. Do you have an Alk test kit?
Actully my water is pristine all tests are perfect.Why do u think the open brains not doing good all my other corals are doing amazing.I tested my water today and everything was perfect