Help! Rene the Bristlenose Has Blisters!

Poor Rene the Bristlenose catfish has what look like skin blisters of varying sizes (1-3mm) one or two on each side lower down under his fins. His abdomen also looks bloated. I have done a water change today as the main advice I read online is to do this. I think he may be sensitive to the anti-bacterial drops I’ve been putting in the tank for the last 4 days (5 day treatment period). If this is the case, I am hoping the lumps will heal when I stop the treatment. I’ve been adding Waterlife brand Myxazin which contains Formaldehyde 0.12% w/w, Malachite Green 0.085% and Acriflavine Hydrochloride 0.055% w/w. I have used the full recommended dose for the small tank with 4 x Sparkling Gouramis, and HALF the dose for the main 200L tank as I know the Bristlenoses, Corys and Suckermouth may be sensitive to the stuff.

Any words of advice would be appreciated. Should I dose the tank tomorrow with the last day of treatment or skip this to see if Rene recovers? I’ve found it difficult to find information online on this specific problem. These fish get a bloated abdomen when they are experiencing kidney failure but I’m hoping it’s not that bad and why the bubble blisters?!?

I have posted a photo of Rene, one blister shows as a light grey blur. I’ll add better photos.

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