Craters after applying second coat of resin

I recently applied a second coat to three of my wall art projects. I sanded each with 120 sandpaper. I wiped the dust with a rag then wiped with a tack cloth. The rag may have had alcohol or acetone on it a some time. It was dry when i used it to wipe the dust off. After applying the second coat craters began to appear on all three. I was creating circles and appeared to be pushing the resin away. Could the possible rag contamination be the cause. I am going to wait a few days and try again. Any suggestions is appreciated