What can cause coral to suddenly stop growing?

About two weeks ago I noticed my corals stopped growing. My parameters are right where they should be. Nothing has changed to the tank. The only thing I can think of is, my McCoskers wrasse is gone, again. I think it may have died and maybe it is having an effect on the tank. OR, since it's fall now, our natural gas furnace has been running for 2 or 3 weeks now and maybe that's having an effect on the corals.

I also recently cleaned my koralia power heads with vinegar. I rinsed them well, before placing them back into the tank.

I should add that two weeks ago, I noticed my forest fire sps and green and orange montipora corals, started to look really unhappy and it even looked like some polyps came off. My acros seem fine though.

Any ideas in this?

Oh and I want to ask. I use RC salt for my reef. I used to use RSCP, but wasn't impressed at the time. I still have half a bucket of both. Can I mix the two salts next water change I do, or is that a no no?

 

Check your PH level.You can mix the 2 but not now.Stick with what you are currently using until you can figure out what the problem is.Vinegar shouldn't be an issue.

 

And no nitrate spikes? Temps are the same in the tank? Calcium and Alk have stayed up/good?

 

I am also curious about alkalinity. That is the stunner when dropped in my tank.

 

Alk, 13

 

Temp always the same. Cal 450. Alk 13. Hmm, I should test for nitrate...

 

And your PH level.........

 

Also what about ammonia ?

You said you think your wrasse died

 

PH 8.4

 

The alk seems a bit high. That could raise the pH too. If you have alot of algae, the pH will go even higher during the day when the lights are on.