I need help medicating tail rot

[Sageofstupidity]

In my 40 gallon 2 of my fish appear to have tail rot, a molly and a juvenile guppy. My corydoras and kuhli loaches look ok but I am worried about medication hurting the scaleless fish. I have maracyn-2 and need advice on how to medicate these fish, do I use half dose on the whole tank? Full dose? Remove the scaleless to another tank while I medicate? One of the corydoras is missing a barbel and it does not seem to be growing back, if that changes anything.

 

[Thyra]

I have never treated fin rot, nor see it (Thankfully) but I noticed on this forum several people have mentioned having it. I just looked it up and this might be helpful to you, if you haven't already seen it: How to Get Rid of Fin Rot