Green Slimer brown and closed up

[prios01]

I'm having the same issue with my green slimmer. Here are my stats JBJ45 with Hydra 26 I just started using a Hanna for my PH, before was API :

 

[Dfrashid]

In the last month I've lost a few SPS corals.

Some are fine, some are unhappy. Birdsnest is about the only thing growing. I've had this green slimer for 3 months now, and it hasn't grown at all.

Tank has been up almost a year now. The rock in it is 2 years old, it was a direct transfer.
1.026
Alk: 7.9
Ca: 400
Mg: 1350
NO3: 1-2ppm
PO4: Undetectable

I dose 2-part in BRS dosers and parameters are kept stable. I dose KNO3 or NO3 drops to undetectable...

Other SPS look "fine", not much growth. The Acro in the top middle is STN'ing slowly from the top. Don't know why either.

Any thoughts here? Shall I try a series of 30% water changes? I'm just afraid of starving the corals with any changes here.

What's your ph levels? I just started controlling mine with kalkwasser and everything started growing like crazy...