normal
Scratches, not so much
Galinstan is a mix of 3 metals, some of the galium is lost from the mix as it seeps into and alloys with the copper heatsink leaving behind a semi solid Al/Sn residue. Initial liquid metal applications really should be checked within 3 months or, if you're dangerous like I am, use more of it than the thin painted layers you see on all the howto videos, bead it up a bit with your barriers in place of course, foam, nail polish, tape, etc
The stain is an extremely thin layer that you can sand off if you want, but it's just cosmetic so there's really no point, especially if you are reapplying liquid metal
Was it really dry looking when you opened it up? The solid flecks of residue might have been dragged across the gpu die as the heatsink was removed and may also be messing up the fit afterwards leading to the bad temps