You cannot charge or ask extra money for the extra utility usage since this would be a unilateral change to the contract that you entered into with the tenant. You are only allowed to increase the rent by the guideline amount once every 12 months and you are also required to serving a 90 days notice N1.  

The same goes with the extra people living or visiting, unless there is overcrowding according to the local municipality, tenants are free to have as many people visiting/living with them as they please.