Huge difference in sustain in a single string?

Hey all,

So I've got a weird issue I wasn't having before, at least not to the point of noticing it. The guitar is a stock Schecter C1 Platinum, I set it up with low strings (D'Addario NYXL 12/60) and tuned it to A# standard. This was ages ago, and while it plays fantastic, I figured it was time for a restring and some love and care. Same tuning, same string gauge, same brand, same everything. Literally nothing changed, except the C# string (the G string in standard) now has shockingly low amounts of sustain even unplugged and acoustically.

It's not happening on the strings that are higher than it, nor the strings that are lower than it. I loosened it and checked the nut and the bridge, nothing there that might be causing an issue. But this wasn't what it was like before. It's got near perfect intonation, it just stops vibrating really damn fast.

Any solutions?