My teen DS has a reusable water bottle he carries everywhere with him. He rinses and refills but hasn’t been leaving it for me to wash properly and I’ve not thought about how long it had been since it was washed out properly. Today I took it from him to wash and it had a layer of black slime inside the spout. I feel sick. I feel like I might have damaged his health by neglecting this. He only drinks water and I didn’t think about anything growing on it since it’s constantly rinsed and refilled. He’s got an awful cough at the moment - did I do this?