Strange, since Mr.Clean sponge sounds too expensive for just melamine foam. Of course, I cannot compare products but here, in Poland, regular melamine foam sponge costs around $2 for pack of two. For my AR removal I used the cheapest available, of Chinese origin, where you get almost two sponges for $1.
On the other hand, the AR on my PloProf was of that "very soft" kind, really easy to get scratched so easy to get removed, too.
Tuco, try to wipe the crystal with microfiber to remove all residues. Colors etc. - sounds like the remaining AR on internal side is working.