Homedog98 - thank you so much for responding!!
I've got 5 other mollies and 3 zebra danios. No sign of any of the others being ill.
I'm in the UK so can't get any aquarium salt until tomorrow morning
can't believe it's gotten so bad. Have taken advice from websites but doesn't seem to help. Will try the salt though.
Feel so awful watching him. He must be in so much pain!
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