"A 401(k) plan recently changed investment advisors, resulting in lower investment advisory fees. However, due to an administrative error, the plan's recordkeeper continued deducting the prior (higher) investment advisory fee from participant accounts for approximately three months after the transition. The recordkeeper has indicated that it was unaware of the fee change when processing the deductions. What is the appropriate method for correcting this error? Specifically, should the recordkeeper (or another party) restore the excess fees to affected participant accounts, and are there any ERISA or other compliance considerations that should be taken into account when making the correction?"