Double treating

I am currently treating for ich but have noticed that one of my fish has got a sore on its side, as if it has scraped itself on an ornament or something. I would like to treat with some Melafix, but can I do that while I am dosing for ich too.

Second, is it ok to carry on treating for ich longer than recommended on the box? I want to make sure that I get rid of it this time, and treatinf for the normal time didnt work last time so I was thinking of treatinf for a fortnight and not just a week.

I think it is possible to dose for longer if symptoms are still there, but if you still had ich after two treatments wouldnt it be better to change whatever you are dosing with?

The meds I use state that if a second dose is required to do a water change & leave a 3 day gap. Melafix is safe to use with other treatments