If it's flashing at the seam areas, then wouldn't that be a drywall issue and not a paint issue? I used to use the Pro Mar 200 for ceilings until about 6 months ago when I started noticing flashing problems and I began to have issues with roller marks as well and the paint was just drying down poorly and not to my satisfaction. So, look at the ceiling and try to determine if it's just looking bad all over or just at the seams directly. If the seams are actually a hump or a depression (perhaps recieved too much mud or not enough) then the light coming in through windows will certainly highlight this. If you decide that it is an issue with the paint, then I really doubt that applying more coats will solve the problem. The best shot you have at making the ceiling look better is to prime with something good and then apply one coat of flat paint over the primer. The better the primer is, the better job that primer will do at sealing the surface. The better the surface is sealed, the better that topcoat will look. The trick to really making a ceiling come out perfect is to have the entire ceiling wet with a full coat of paint at the same time. Painting with flat over primer is way better than painting flat over flat.