Sps will lose color for numerous reasons. Maybe a little info about your tank and some pics might help. How long have the acros been in your system? Lighting? ...Things like that
When was the Last time you've done a water change? How many fish do u have? My guess would be bad water quality (high phosphates/high nitrates) mixed with unstable alk.
Still tough to say. You didn't post your parameters. Did you acclimate them to your lights? Did you have any swings lately? I'm assuming you mean 1.028 SG. How did you measure it? Has that changed drastically lately? At this point it could be a number of things. The more info you give the more we can help you figure it out.
I had a red Dragon that was losing its color when I first put it in, lowered it down and it sprung right back, I would start them low, but most importantly make sure your system is able to handle SPS by answering the guys questions.