Anon, review your contract as LS advises. However, generally there is nothing preventing you from closing the accounts for inactivity.
It would be advisable from a PR perspective to a send a notice informing them you are closing the account and if they wish to keep it open they should contact you.
Under the definition of adverse action in Reg.B closing an account for inactivity is not adverse action therefor no AAN would be required.
The opinions expressed are mine and they are not to be taken as legal advice.