KCD,
It is called "weeping" and somewhat common when there is water behind the gunite. Most plaster companies will not plaster if the weeping is too bad. Took me about 4 months to solve my weeping problem.
The right solution is to divert the water that is behind the gunite to go somewhere else. You can't block it, it must be re-routed or removed.
In my case, I have a sump pump that runs 24/7, even in the hottest Texas days, that pumps the water out. Unknow to anyone at the time, my pool was built in the middle of a small underground creek. Sigh!
Thanks,
Jim R.