Help! Rock flower anemones dying?

[LesPoissons]

Hi all,
I have 4 rock flower nems in a 220g, going on a year or more. This week the red one curled up and is gone and now my green is going too? Its tentacles are all rolled in? Any thoughts? My zebra one just above it and to the right looks totally fine and I have a tiny orange that also seems fine so far. A week ago the green was fine too though?
Nothing has changed in my tank over the last year other than increase in mag recently (it was 1200s, put it up to 1600 and now it's coming down.) And a slow increase in lighting over a year from 35% to 74%.
1.026
Ph 8.3
Temp 79
Cal 420
Mag 1500
Alk 8.4
Dkh 3
Nitrates 2.5
Phos 0- 0.05

 

[Hitman]

Do you have any butterflyfish? Some have been known to nip at them once grown up is why I ask.

 

[LesPoissons]

Nope :/