Came down this morning and opened their cage for them and nothing happened. Usually they are already up and waiting to get out.
I found them both dead in their nest, tucked up like they were sleeping. Yesterday they had been perfectly happy, drinking and eating normally. My initial thought was to check the gas cooker but that is fine, and I have turned the boiler off just in case (got someone coming out to service it).
It seems very odd that they died together. There as nothing out of the ordinary in the cage, normal food and water. Could it have been anything else, if we don't have a leak?