Would be more prudent to know what exactly it is.Melafix is anti-bacterial,Pimafix is anti-fungal.
They are organic and not really considered meds...they just inhibit and weaken the causing agents where the fish's own immune system can get a grip on it.More of preventatives for when infection could happen (like injuries) to hold things down while the fish heals than meds to get it under control after infection's grabbed hold.
You can try them together (along with salt treatment) in conjunction as an initial broad spectrum approach.Shouldn't damage bio-filtration. It should only be stop gap measure until this is correctly identified though.
I can only say what I think from your desciption,which is a scale was knocked off against some decor probably minor damage to flesh which let bacteria from the decor in.Without pic,I'd say Columnaris.
Just think about it.