Is it normal for a LiPo's voltage to drop significantly over a 12hr period?

I balanced a (2S) pack yesterday and both cells finished at 4.2v as usual. I didn't get to use it as planned, so I hooked it up to my charger to discharge it for storage. As soon as the charger started, the battery was in the 7.5-7.6 range. Both cells were within .01v of each other. Is this normal?

No - that doesn't sound right at all. They should hold voltage better than that - unless you were discharging at a really big rate like 30, or 40amps. You should've discharged a significant mah to get down to that voltage. What capacity, how many cycles on them??

Lipo has practically no self discharge. I got a pr of pacs for a project that never happened and they're right at a yr old (this month) - I've been measuring voltage at least once a month - went from 11.4v to 11.1v in a year.

It's a 5000mah 40c pack with 10 cycles max. My charger only discharges at 1A max. I'll do some further testing after class.