"My fancy German hydrometer called them 1.285-12.280 brand new from the store."
Ok, so that is right. You then pulled them down by 20AH, which is not much, so they should be doing better. So the question is - how did you measure that 20AH? Perhaps it was more than that?
The big question is what is the SG now? If not too bad, then we have to question the other numbers. Mostly, believe the hydrometer.
Another thing about voltage drop is where you measure it on some wires to a meter. Long and thin wires can give you a bigger drop than taken right from the battery posts.
