paint too thin or too much?

i was airbrushing my r33 gtr....and after priming and painting steps i noticed it had small orange peel....so i sand it down with 1200, rinse it and dry it for another coat of paint...how ever this time the paint wnt sit prply on edges...i can notice it because i can see some of my white primer under and the paint just wnt cover it....is my paint too thin there fore its running down or did i just spray too much?