foxface fell really sick this morning and is currently layed against rock work “camouflaged” all other fish are fine added purple tang and cleaner shrimp 2 week ago everything was fine until now only thing that’s happened is water change yesterday that swang salinity from 1.026 to (now) 1.024 PH is same as previous check (8.15) and NO3 is low at 0.5 i cleaned the skimmer yesterday with white distilled vinegar but rinsed throughly and let skimmer run in 2 new buckets of water before adding back into the tank but ran all night and apparently he was fine this morning according to family and now not even moving I’ve turned the lights off to help stress and have a jug of RODI water for a dip but my concern is this will stress him even more and that will finish him off any chance of survival and what should be my next move?