Varnishing over mixed media?

Hello This is my first post, and I was wondering if I could call on your sage advice. I've never really varnished my paintings before, never really saw the point, until now, when I'm preparing some paintings to enter into my first exhibition. I paint in acrylics on canvas mainly, but usually with some mixed media elements (often PVA glue and beads). I just tried varnishing my first mixed media painting. I nearly had a heart attack when the part of the painting with PVA and beads went milky - I thought at first that it was smearing the paint underneath, but my husband assured me it was just the PVA dissolving and that it would all dry clear again, which it is beginning to - whew! BUT, I'm noticing sort of cracks or pools forming around a few of the beads where I think the varnish and glue are reacting or interacting or something. I don't think I like it terribly much, though it's very fine and not really noticeable unless you look very closely. It may yet dry invisible, for all I know, it's still drying as we speak. Does anyone have any tips on varnishing over PVA or mixed media - things to avoid, things that will interact badly? The painting I'm on now is a smaller, less prominent painting, but I need to varnish a bigger painting next, which is half covered in PVA, so I'm nervous about varnishing that one until I understand the effects of varnish on unconventional art materials a bit better. Thanks in advance.