How old is the tank? How long have the sps been in it? Are they colonies or frags? If you are not using GFO, I would definitely get that going. Be careful with the GFO if just starting out with it, it is powerful stuff. You might want to simultaneously start lowering your alkalinity to around 8 dKH to get it more in line with a "low nutrient" tank. How are you supplementing Ca and Alk? Ideally, IMO, a Ca reactor is the best for this if your tank is mainly SPS. If dosing two part, then dosing pumps dosing maybe 10 times a day is ideal. There is a little acronym I like to remember; "SPS" stands for, "Stability Promotes Success". Keep everything consistent. The other thing I would suggest is adding some actinic lighting. My preferred actinic supplementation is VHO using the URI Super Actinic R bulbs. Put a couple of them up there some how. Maybe mount them with a reflector off of your pendants. Kind of like "wings". Then just sit back, be patient and watch that tank take off.
HTH
Dennis