John,
It's a good thing you put some gloss coat under the decals, but sometimes they silver anyway. But if it's only under certain angles, it might just be a difference of "reflectability" between the decals and the underlying coat. Anyway, if the decals are not overcoated, the thing to do would be to find a compatible decal setting solution and try to use it, and after everything is dried throughly, to overcoat the whole model (you have to mask the clear parts, if any are present. then it should give you this "painted on" look everybody is lookin' for. Hope it helps, have a nice day
Paweł