What is a landlord's right to raise rent due to a lease violation?

1) If there is a written lease in place, you cannot raise the rent during the term of the lease (unless the lease itself states that it can be raised  under certain circumstances.)

2) If you feel that the tenants have materially violated the lease, then you could bring an action to evict them--that is the remedy for a material, or significant, lease violation. So you can leave them as tenants or you can evict them, but you can't raise the rent mid-lease. (When this lease is up, you could refuse to re-rent to them, or propose a much higher rent.)

3) Note that if you told the tenants they could put in a wood stove but did not at that time put limits on it--i.e. you simply told them they could put in a stove, but did not tell them it had to be with your knowledge and pre-approval--then they have not done anything wrong and you most likely cannot take any action.