guys i could use some help!

first coat applied to alitte to thick. so i let it dry for like 4-5 days. then i knocked it down with 400 wiped it down with mineral spirits let it dry then blew it off with airhose then applied 2nd coat much thinner then first. this was at 8:00 last night. Got up at 3:30 am and went to put another coat on and it started lifting up in small spots . I guess you would call it checking . to me it looks like the paint is cracking then it just lifts and gets all flaky. Its just small spots the size of a quarter and just a couple spots . I guess they can be knocked out with 600 when it drys good but wont these spots need to be sanded down more then the rest of the panel. This is just a practice piece so im learning as i go here. Im using profesional tint base stuff turquos. orderless mineral spirits also. im not having any trouble with bubbles or soft paint. my first heavy coat went on thick but once it died it was hard as hell. could it have been the air hose blew something on the panel before i rolled the second coat?