I hope the OP quarantine his power blue tang. 45 gal for PB is too smallSo you have alot going on here. First off, your birdsnest coral is bleaching. If you had a nem get destroyed, it has now destroyed alot of your micro fauna in the tank. Nems deteriorate super fast. You should do a 50% water change and run some carbon before it kills the rest of the life in the tank. Your tank is super clean, this leads me to believe its not very old yet and needs to mature a little more before you decide to go into alot of corals. I would also suggest researching everything you put in this tank heavily, not even gonna start on the powder blue in there.
Research every single thing you are going to do to this tank in the future, every fish, coral, bottled chemical, food, salt type, heater type, even your filter media.
RESEARCH EVERYTHING