Non-renewal of Tenant

[Hope S.]

I have a tenant whose lease expires in a few months.  I have had several issues with this tenant that I was willing to let go, but most recently I found the unit listed on air bnb and it is explicitly prohibited in the lease (although we never discussed it, this is an inherited tenant).   I would like to just let them know we won't be renewing.  Would you explain reasoning or just supply a simple notice of non-renewal?  And am I overreacting with the airbnb being the final straw?