You could always irritate the monk and say it is a *magical* disease, so the paladin is OK but he gets encrusted
When this came up in my game I rules that the paladin was immune, the spores couldn't get a grip on him. I think in future I wouldn't have him immune but would allow him to use his remove disease power to kill it, since he otherwise doesn't get much call for that funky power.
Cheers
