I have a small 3 gallon pico all coral tank on my desk that’s been up for about a year with no issues at all until about four days ago I noticed some coral missing, I kept watching thinking since it was just my tiny bit of pulsing Xenia it was whatever but when my green hairy mushrooms in the front disappeared I took action and did a complete 80-90% water change, I tested the water yesterday and everything was in perfect parameters other than my phosphate on the API reef master kit it said my phosphate was 1.0ppm. I did another water change about the same amount and retested it and now my phosphate is between 0.25 and 0.5 ppm. But my GSP wall has continued to wilt away. What is happening and what else do I do?