Sounds like the couple are fairly new tenants to your property. I would toss them out.
Not necessarily evict them, but give'em the, "...Hey, I think this place is a little too expensive for you and your husband's budget right now. Let's get you moved into something cheaper that would give you a chance to get your finances in order...". Words to that effect.
You want to get them out of your hair since they have already started down the path of, "let's see how much we can get away with". It only gets worse. It's best to stop things now before it does.
Most tenants follow a pattern - the legal system actually helps them (in my opinion). Once a tenant knows how to work, "the rental cycle", they get better at screwing you out of money. It could take months to get them out of your property using legal methods.
If this was an established tenant, with a solid on-time payment history, have a one-on-one chat with them and get to the root of their problem. It may just be temporary. Bad things happen to good people, but you have to get to the true cause of their issue.