Keep your system stable and do a much larger water change. I would turn off all of your pumps and powerheads, stick your arm in and swirl up as much as possible and siphon it out. If it really bad, and you need to remove alot of water, put a filter sock on the end of your siphon hose so you can put only the water you absolutely need back into the aquarium. BRING YOUR TEMP UP. 72 is VERY low.

Keep up on your water changes, especially if you do not want to lose your SPS. Salt is cheaper than coral.