Steven Van Dyck
Did you put the decals on a gloss surface, and did you prepare them with some solving agent? That can protect against silvering or loosening like this. I also have some white detritus with varnishing using Vallejo, but this I remove manually. That only results in some tiny bits of gloss coming through.

Bruce Huxtable
Really liking your painting of the small details, so I'm keeping everything crossed that the few blemishes will be resolved easily.

GCB Author
Decals were perfect: no silvering after applying them with Micro Set/Sol.

I used:
Primer: Mr Hobby, finishing surfacer 1500 black
Paint: AK real color Halo green thinned with AK thinner
Gloss varnish: Mr Hobby Super Clear (spray)
Decals: Caracal decals applied with Micro set and Micro Sol
Weathering: oil (Abteilung)
Light matt varnish (Mr Hobby Super Clear).
Until there, all good. You can partially see if on the picture above.

Then, final varnish: VMS Matt applied directly from the bottle (no thinner) and got all kind of silvering and white marks. I guess that the VMS varnish reacted with something, but what? Model is lost now: tried to remove decals, and a mess.. Any assistance appreciated.

Steven Van Dyck
In stead of Micro Sol I now use Daco Sol, that would be stronger (it's available in 3 variants). I saw that some brands now sell paint removing agents that don't damage the plastic, maybe you can try to partially remove the worst affected surfaces, but I don't have experience with these. Another thing you should try is to spray a new gloss cover, this sometimes removes the discoloration. The final layer I'd always spray in stead of brush applying.

CaptGPF
For silvering, I sometimes found that applying Walther's setting solution, poking the area to let the solution fill in, applying a bit more solution and then rolling a cotton bud to press it down fixes the problem. The challenge with Walther's is that it's REALLY strong, so if you get it on the paint itself, quickly wipe it off.

For bad silvering with lots of spots, that's going to be a lot tougher…

GCB Author
Thanks, but the issue happened only after I applied the VMS matt varnish. Before, there was no silvering.. I guess there was a chemical reaction