Answer:
With respect to consumer accounts, if you accept those checks for deposit and then charge customers for the fee, you should send these customers a 30-day notice of the increase. During the 30-day delay period, if you accept a check for deposit, you'll have to absorb the difference in fees.
For business accounts, any notice period is a matter that should be covered in the deposit account agreement.
Unless there is a state law or regulation limiting such fees, there's nothing to my knowledge preventing you from up-charging for foreign check collection, if you make proper disclosures.