@Richard Ma
1. Comply with the order from the City, or you are likely to face fines
2. You cannot kick them out; cities have reasonable standards for issuing citations, so you have a problem
3. Sounds like you may need a new fridge - the city isn't issuing a citation because the tenants are dirty, they are issuing a citation because they suspect there is an underlying material cause beyond use
4. Get a pest control company out & make sure they are licensed, otherwise, the city won't back down
If you attempt to kick them out now, you are likely to look retaliatory, which is always a problem.
Tackle the issues and be more active on site for the balance of their tenancy; the more they see you, the fewer problems you are likely to have. Last, issue a written non renewal notice 60 - 90 days before the end of their term and provide a legitimate reason. Call them after you issue the notice and let them know that you appreciated their stay, but that for a variety of factors that are cited in the notice you need to move in a different direction.
None of this is personal for you, this is just about your asset; act accordingly.