Every set I've had have swelled. I also use SXT on black carpet. I've tried naptha, brake cleaner, and just sxt for cleaning. I never let the cleaners sit on the tire, it's always apply and immediately wipe off. The worse swelling I had was when I was using only sxt to both sauce and clean after a run. To sauce, I applied about 5mins before a run and wiped enough back off so it would be almost totally dry before I ran. I think I'm going to try a new set and just use either naptha or brake cleaner to clean and skip the sauce. Just sucks because I know traction will be crap.
Something I have also noticed with these tires: after a run, they are the worst I have seen to gum up on the edges. Takes quite a bit of cleaning to remove. Maybe this is why they swell so bad? Could be that I am having to clean them too much?