Corals turning almost white

[whatcaneyedo]

I'm thinking that your lighting has a lot to do with your problem as well. Watts per gallon doesn't mean anything. Most people stopped believing in that in the 90's I think. What you want to look for is intensity and spectrum. Regular output T5 bulbs like what you've described are meant for freshwater tanks or maybe fish-only saltwater tanks. However the vast majority are marketed for freshwater period. If you want to sustain and grow coral you need (high output) HO T5 bulbs, metal halides or LEDs.

You also want to target full strength seawater which is 1.025. 1.023 is a little bit low.

How much flow do you have? You said 'high' but that can mean different things to different people. So how much in terms of gallons per hour?