Sps wants:
High light (proper spectrum)
high water movement
Stability (not moved for long long times even if it's not responding).
Heavy water changes and proper 3 part dosing.
Very low PO4. If you can get phosphate into the Parts per billion, instead of even the parts per million, you'll have better colour and growth.
Good salt. That's why I stick with RC, I had lots of weird problems with sps until I changed to RC and never ever put any other kind of salt in there. It also comes back to Stability above. Pick a good salt and stick with it forever. If it's a "new" salt to market look into the company making it. If it's a new kind of startup, avoid it, they might be out of business next month, or they may decide not to ship to Canada, or who knows.
Check your parameters, all the answers are in there. Get good test kits (digital ones if possible), some of the match-a-colour ones can't possibly give proper readings in ultra low nutrient systems.
Basically, if sps can get lots of food from the water (Phosphate for example), then they brown up and stop getting food from phtosynthesis. The more you "starve" them, they will then go to the light source. If you have high nutrients, and crappy light spectrum, you're going to get very brown sps. That's why I push GFO, DSB, very light feedings (I feed the fish maybe twice a week) and proper quality LED lights (the first batch of wallet-friendly chinese led's were sadly lacking in proper light wavelength output, they're likely better now). As well, the light setting that makes the corals look amazing may not have enough full spectrum to make them happy. I run all lights at max capacity from 11am-4pm, at which time I switch to ultra purple T5's and mostly UV and ROYAL BLUE LEDs. Corals look like crap under the whites, but may they pop under the blues.
