Troublesome tenants

Other

my sister and I own a 5 bed HMO in Salisbury and its lovely, we look after it well. We have two long term tenants, two individuals not a couple, who have been there since we started it 4yrs ago & both have complained about 2 of the current tenants both young single men. They leave the lights on 24/7, use the washing machine & tumble dryer to the exclusion of anyone else, leave their laundry in the kitchen, including their girlfriend's washing, have their girlfriends/male friends to stay frequently and leave the shower and kitchen dirty. These two men have one year tenancies we signed in December/January. Had we known how much fuel would increase we would have increased the rent of the newcomers accordingly. What can we do?