No thermostat and not sure of temps you keep at - that quite possibly sounds like your problem right there! Put it this way, inside today, my heatlights were off most of the day. If your 8 week old was getting additional heat inside the enclosure, its very easily overheated. Yes, food is also too big, it could be impacted.
Did you research before buying your beardie?
You need to buy a thermostat and get your heat sorted mate.
