Sounds like an old set of decals. This may be barn door after the horse, but if your decals are in any way suspicious, you should do a test with a decal off the sheet that you don't need. If the results are less than satisfactory, go down to your LHS and get some Microscale Liquid Decal Film. you can apply this fairly heavily with a soft, clean brush, work it around to the edge of the decal, and let it dry. It will dry completely level if you don't try to work it too much, and you still have the bonus of having a seperate decal to work with, unlike spray gloss coats that 'fuse' everything together.
Of course, if it is an OOP kit, replacements can always be bought or made by one of the custom decal makers such as myself.