Relative humidity can really raise Cain with airbrush acrylics too. I use clear gloss as a top coat and often mix my color shift pigments into the clear to go over black or transparent black laid across the back. These are usually wet coats and I have to heat set them pronto or the black underlayment will slip. If the relative humidity is high I have used the hairdryer on high heat until the paint is matte in appearance only to have it sop up the wet in the air and do fun things. I think you've had some serious moisture of late and if so I think that that is half of your issue Sarge. I'd give them extra time with the blower, then hang them in a warm, 190 degree, oven for an hour and see if that helps bind your splatter coat better.