Locked 4200's HELP!!!

[philly]

Hello.
I have 3 packs of matched 4200's. 2 of them have some how stopped holding charge. I charged them the night before the York regional and topped before they went in the car, and they lasted till the second corner!

The packs are about 3 months old and have been used maybe 6 times?

I'm hoping it will be a case of fully discharging and then starting again, but what is the best way to go about this?