Some chargers can recover over discharged batteries - down to 2.4 or so, I think. Whether it's safe to use them thereafter is another question. The low charge can damage them and make them unsafe, so it's better to do as
@daviedog did and recycle them.
Our resident battery expert, Mooch, has a post on when to retire batteries:
When should you replace a battery? | E-Cigarette Forum
The short version is it's time to recycle when:
- The battery does something odd
- Something happens to the battery - it gets overheated, physically damaged etc.
- You notice a difference in performance - the charge doesn't last as long, or it can't perform in high-power applications
If the drop in capacity is really borderline - you said "maybe" it had dropped - you're probably OK for a bit. If you've definitely noticed a decline in capacity then it's time to move on. The lower capacity itself won't do you any harm, but it's a sign that the batteries are aging and some of the other aging mechanisms could be dangerous.