It really looks like ich in my opinion. the white spots can come and go. My clowns showed the same blotchy skin when you weren't seeing the spotting. Read Beths treatment for ich.
I did a hypo treatment in a qt and left my dt fallow for about 40 days. The fish came through like champs and I'm back in business. The hypo treatment is a bit of a pain, but it was worth it.
You will read on here that others have had luck with chemical treatments, but that seems to be hit and miss.