You will have to add the med to the main tank then.
Just make sure the spots don't look like a cluster of eggs, berries, or cauliflower.
I wouldn't panic yet. It dosn't look like lymthocystis, but we do need to rule it out.
I would try the bacterial med first.
Lymthocystis can also look like smooth lumps.
When fish get lumps, bumps, or spots filled with fluid, it's best to issolate incase they burst.
This is a pic of a smooth lymthocystis lump.