Tenant installed W & D racked up 1000 water bill

So our elderly couple (65-70 range) tenants who work as caregivers for a senior living facility installed washer and dryer in the unit without consulting us. They said they didn’t want to contract covid19 at a laundromat which we did feel. As a result we got 1500 water bill (usually 500) which we didn’t feel!! What would you do if you were in the situation? It is a rent controlled unit and the rent is a little less than 1050 and market rent is 1600-1900. They pay on time and keep the place clean. But it was a big deal breaker for us when cash is not flowing with this low rent.