Not Just Yellow
Photos from google images
Yellow fungus is a deadly fungus that is highly contagious among bearded dragons. This fungus is slow growing but eventually will kill a bearded dragon. There are treatments for this fungus, but there is no cure. The fungus is not always yellow as the name suggest, it can also be various shades of brown, tan & black. It slowly destroys a dragons skin and causes a dragon to become inactive and stop eating. If your dragon has odd shaped patches that are off color, seek a reptile vet's opinion as soon as possible, but please don't confuse discolored skin with shedding skin.