So in my tank I have a foxface and blue tang amongst other things.

My foxface frequently deposits what I guess are eggs, but I could be
completely wrong. It's granular and whiteish, for all I know it could
be sand, but does not resemble standard detritus. The other day whilst
observing my finned friends I saw my blue tang(hippo tang, regal tang,
dori from nemo...etc) doing what appeared to be going #3 on the alleged
eggs. Is it possible that they were trying to get their procreation on?
Is cross breeding possible? Am I witnessing something else?