Very good work, overall. Looks like the decal film around the unit insignia on the front has silvered a bit. With waterslide decals, you need to apply a clear gloss first, then apply the decal with a solvent solution sold for applying decals (Micro-Sol, Micro-Set, Solvaset, or the Testors setting solution). This will melt the film into the surface. When it's all dry, overspray with another clear gloss coat and then weather the finish. Finally, overspray with clear flat to kill the shine (any clear parts must be masked during this step, as clear flat will fog the transparent plastic).
If you skip these steps, you will have a fine layer of air trapped under the decal's clear film, and this will appear silvery under strong light.
If you find the decal has silvered despite your best efforts, you can repeat the application of the solvent, and prick the decal's surface with a pin to allow air to escape as it dries. If that still doesn't work, just use a fine brush to paint over the film with the vehicle's base color (in this case, Olive Drab).
Some builders prefer to use rub on transfers (like those produced by Archer and Verlinden) rather than waterslide decals. This avoids the problems of decal film altogether.
With the clear molded headlights provided by Dragon in their current Shermans, the key is to paint the back of the light silver, then mask the lens and paint the whole light Olive Drab. When you remove the mask, you'll have an Olive Drab housing and a clear lens with a silver reflector inside.