Give them two options:
1. One of them volunteers to leave. They negotiate whatever funds exchange hands, sign a termination agreement for that one tenant, and that person leaves; or
2. Kick them both out.
Tell them to make a choice and move forward. One goes or they both go but they can't both stay.
I have a "Remove Tenant" addendum that stipulates who is leaving, when they are leaving, that they give up all rights and responsibilities to the property, and that the deposit remains with me so they have to negotiate finances on their own. It also notifies the remaining tenant that they are fully responsible for rent, the condition of the property, etc.
How about giving all tenants the option that is they move out by the end of the month and leave their room in good condition, you will allow them to break the lease without charging any fees and return their security deposit. Let them know they seem unhappy and that you want your tenants to be comfortable in your property so you allow them this one time opportunity.
Hopefully at least one of them will take you up on your offer and then you can replace them now when it is peak time to find tenants. If they refuse your offer let them know you can’t get involved in personal disputes and to work it out among themselves. You can then remind them of your offer. After that I would not respond to their texts, calls, or emails with complaints about each other.