Issue with my koolstops

So a couple months ago I switched to koolstop mtb pads (vbrake) front and rear and have been really pleased with the performance. Even riding in rain and through deep mud has been fine with these.

A couple weeks ago I had a race, one of the braking zones happened to be in a creek crossing, and since that race I haven't been able to get my brakes to function as well as they did beforehand. Then, to make matters worse, while I was riding today they seemed to lose almost all of their bite plus squealing/chattering a lot more than normal.

This has been kinda an ongoing problem since that race so I've cleaned the rim and pads, and hit the pads with some sandpaper to remove any glaze that might be on there. The rims are some generic alloy guys, so I'm not real sure if getting them with sandpaper is such a good idea, maybe a brillo pad?

I'm pretty much at a total loss here, but have a race this Sunday, so I need to solve this problem fast.

Thanks

Rob