If you go to "Wireless > Configure > Radio settings > RF Profiles" you can either edit or create a profile and either set the radio power, or set it to auto and let it automatically adjust based on neighboring APs.
@nst1 Are both access points broadcasting the same SSID's or are they broadcasting different networks?
Either way Wireless > Radio is where you need to go the change your settings.
If you only have two MR42's you don't have an issue. They are highly probably to choose two non-overlapping channel sets, and will not impede each other.