Can anyone who's been there talk me through this?

I think I figured out why my mostly EBF 12-week-old daughter has been really fussy and reluctant to take bottles--finally did a taste/smell test, which made me feel like a cannibal btw, and while I thought they both smelled gross, the frozen/thawed milk had a nasty, plastic-y/soapy aftertaste and the freshly-pumped didn't. When I've been away for appointments baby girl will take the first bottle I leave with the sitter (always the fresh one) and then reject the later bottles, usually from the fridge that were pumped in the past day or two. I'm trying to determine whether it's really high lipase that's the problem or if she just is developing a bottle rejection issue (which would be a serious problem because she's starting daycare right after the holidays).

So, does it sound most likely that my huge frozen stash is all tainted with high lipase and I have to scald immediately and start over? I read that you can still donate high lipase frozen, but is that gross and rude, or actually helpful? Also wondering if high lipase is consistent with the mother through multiple babies, or if it's possible to have it with one baby and not with another--my son, who's now 2, never had a problem at all with the next-day stuff or the frozen, he was a total milk monster. New baby is a terrific nurser and gaining very well, but is rejecting this milk.