Many of the rules which apply to boards should also be in effect for committees. Concepts like term limits, confidentiality and conflict of interest are equally applicable to the committee. A simple fix is to have a policy which states all of the board governance rules apply to the board and any standing committees.
The next step is to see who is serving on committees and is not a member of the board? These members need to sign the annual confirmations about confidentiality and conflict of interest. Also, if there is board training being provided, these committee members should be included.
Spend a little time on the terms of reference for each committee. The obligations and duties of each committee should be clear. No one should be wondering if board behaviour is a duty of the nominating committee or the governance committee. Your governance framework is stronger if all the rules apply to committees as well as the board.