I boil in Dicroclean 909 from Brownell's 24# for no a lot, but $20 Haz Mat fee. One cup per 4gal of rainwater for 15 minutes, rinse with rainwater & you're ready to go. 4 gal mixture will usually do 5-6 sets of barrels. I throw it out after that. I had a set go brown on me and decided whatever life the degreaser had left in it wasn't worth the time / trouble of starting over.

I used acetone for a while, but found streaking from the residue left behind.

90% sure that's your problem.