What light are you using/settings? I'm assuming it isn't getting too much light since the nearby blasto is doing well, but also is more center-of-tank, so could be in a hot spot. Have you tried moving it to the side or a corner?
How long has the Acan been in the tank? How long was it doing well? Did this start to happen after you switched to Reef Crystals?
What are you using for dosing Ca/Mg? How are you managing your ALK? Water changes only? Have you tried a more complete supplement like All-For-Reef?
Phosphate at or near zero is not good. That might make your LPS pouty. Might want to dose PO4 to keep it somewhere between 0.03 and 0.1ppm (alternatively, I dose NO3/PO4 just enough to make sure Salifert and Hanna tests aren't completely clear).
How long has the Acan been in the tank? How long was it doing well? Did this start to happen after you switched to Reef Crystals?
What are you using for dosing Ca/Mg? How are you managing your ALK? Water changes only? Have you tried a more complete supplement like All-For-Reef?
Phosphate at or near zero is not good. That might make your LPS pouty. Might want to dose PO4 to keep it somewhere between 0.03 and 0.1ppm (alternatively, I dose NO3/PO4 just enough to make sure Salifert and Hanna tests aren't completely clear).