[Suze65]

I’m so sorry for your loss, what a terrible shock. Personally I don’t think you need to re think your husbandry. It all sounds fine, and the fact that it’s worked well for 10 years is testament to that. As for a fungal infection on the tongue, I would question that, open mouthed breathing is usually a respiratory infection. I think I would find another vet.
Remember, tortoises can and often do hide any signs of illness until it’s too late and die suddenly, it may well be that there was nothing you could have done to prevent this from happening. This behaviour is a survival strategy. I hope this makes you feel better.