Tenant keeps harping about mold

[Carlos Lez]

I rent rooms in a house. I have been managing this one property where everything has been going well and housemates have been happy and even renewing their lease for the past couple of years with no complaints. Now, I have this one new tenant who has been complaining about small issues here and there that have been resolved within a day of two. Then she brought about an issue saying that the bathroom has black mold. We tested it was not black mold and there were light spots with the lack of using the ventilation. That was cleaned up. Now again I have received the following note;

"Thank you for taking care of the mold in the bathroom. I was having a lot of trouble with my P.O.T.S. Syndrome and my breathing and was concerned it was from the mold. I did a take home mold test and found more mold in the kitchen and the vent in the foyer. My mom is concerned and said she can hire a professional company to do more tests if necessary. Let me know what we can do about it."

There is no mold that I can see. However, I am willing to let this tenant go as this appears to be a nuisance. The girl is 18 years old and has a helicopter mom. I know I'll have a vacant place for quite sometime as it is difficult to find people to rent these rooms during this time of the year. 

I am just seeking your advice on how to handle this and not let them feel that I have buckled. I am not even sure if she wants to leave. I just don't understand where this is heading.

Thank you in advance for any advise in this matter.