If they are only one there should be no problem but what ever you do get them insured tomorrow and it will then be 14 days before insurance kicks in.
If you seee a vet before this and there is a problem , you will not be able to claim for it for the rest of there lives.
I agree that in central heating they will get thirstier but at their age I dont think they are ill and yes the fountain is probably also a toy to them.