I don't see anything that looks like yellow fungus either, but I will advise you to take the 3 minutes it takes to reach into his tank and throw out any bowel movements when he does them, otherwise he will end up sick with parasites, worms, or a bacterial infection and will need to see a reptile vet which will take a lot more time and cost money. Seriously, not trying to be a smart ass, but you shouldn't wait over a week to clean any poops out of his tank, that can be very unhealthy to him and to you, especially when his lights are cooking it and putting fumes into the air. I reach into each of my 3 beardie's enclosures once a day, usually in the morning, and clean out any poops, and then if later in the day I see any I pull them out too. All 3 tanks take less than 5 minutes, and I completely disinfect all 3 once a week. It's just good hygiene for him and for you.