Need Help Quick, think my blenny is dying

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Hi there,

I think My Zebra Blenny is on his way out and I'm hoping someone can help me help him. He seemed fine last night, came up to eat and looked fairly happy.

This morning when the lights came on he didn't come out as usual, when he did struggle out from the rocks this is what I saw...







He doesn't swim, more just struggles along the sand. All his movements are very twitchy and erratic. He is "breathing" heavily and rolls over onto his side constantly (I don't know if this is the current pushing him around or what.) I got this fish at the end of may (just before may long weekend) and he spent 4 weeks in a quarantine tank before going into the display. He has seemed very healthy until this morning

Here is a terrible picture of him being fat and happy from July 1



So what can I do????? My quarantine tank has a new fish in it and if the blenny has something I don't want to expose the new guy to it. The other tank's inhabitants are a foxface and 2 ocellaris clowns and they all look great. The blenny spends a lot of time interacting with the foxface (I don't know if it's fighting...sometimes it looks aggressive, other times it just looks like they're hanging out) Could this be a reaction from the foxface sting?

Changes I've made recently: I changed 10 gallons on thursday night, I fragged a hairy mushroom on Wednesday night, and tried a new food yesterday. Everybody had some of that and no one else is showing any ill effects.

I'll run down and do some tests so I can post the ammonia/nitrite/nitrate...
Salinity is 1.027 (with a refractometer)
Ph 8.3
Temp 26 Celcius

Any help is greatly appreciated
Thanks