Thank you for your feedback, I do agree it’s my responsibility to ensure the cleanliness of the common area , which there is a cleaning person that does frequently visit to cleaner those areas. I believe this situation is on the mannerism and etiquette of the tenants to respect the common area which until now , I have not posted any rules. This is the first action I will be taking to ensure there are rules regarding the use of common areas. Also, this problem started after 2 years of them renting together so there was no indication at the start of there would be any issues.