Tank crashing...could it be due to these?

[Son Of Skyline]

Ok here's what I have so far...

Just calibrated and hooked up a pH monitor to the tank (thanks Shane!). As of 9:00pm it reads 8.07. Seems really low so I might go out and get more calibration fluid tomorrow and recalibrate in case I messed up the first time.

Alk: 10.9 dkh...higher than the "recommended" 8-9, but still within normal boundaries.

Ca: 380ppm...normal.

SG: 1.022 with a refractometer...a little low maybe?

Mg: 1140ppm...lower than the recommended 1300ppm so I dosed a little bit of Mg. Gonna test again tomorrow.

Did a 10% water change today, and I'm going to keep doing water changes every couple days for now.

Got some phosphate sponge. It's running through an Aquaclear 150. Pretty small but it's all I could dig up in the junk box.

One thing I still don't understand though, is why only our acropora are being affected. If there were water quality problems, wouldn't it affect all the corals?

That's all for today. The battle continues tomorrow.