Complaint made about noisy coughing/spitting?!

Hi, neighbours next to my tenants have just contacted me to say that one of my tenants coughs and spits into the sink in the upstairs bathroom, late at night and early in the morning for 30-45 minutes every day. The owner of the house used to experience it and now she rents the house and her tenant is moving out after the 6 month minimum period for the same reason. How do I deal with that?! She said it is really loud and she never said anything when she lived there in case it was a medical condition and she expected some disturbance in a terrace house but is worried that he tenants will always be put off by it too.

Have I got the right to approach my tenants about this? She also said that he shouts throughout the day (described as having a conversation with someone in the kitchen whilst he’s in the upstairs bedroom) so I thought I can use that as an ‘in’ to any conversation. I’m assuming this neighbour is very tolerant as this is the first time she’s contacted me and lived next to them for quite a long time and her tenant for 6 months. Any advice gratefully received