Hello bobboman!
to TR and the salty world of nano tanks.
At this time I would not worry too much about the white scum, it is probably the result of the new sand and die off in the rock. What are your tank parameters?
I would worry about the damsels and I too recommend taking them back. As your tank goes through its cycle and becomes established there are many toxic compounds that mount and recede. Damsels are tough fish and may survive this but this is cruel to the fish. Plus you will probably not want these guys in your tank long term, they are mean! in fact they are often called DAMNsels!
