"Shedding" is normal...flaking, though? Is the usage there another form of shedding? If the adf is hanging out at the top prolonged then it is trying to get more oxygen. You may not have enough oxygenation in your tank.
When african dwarf frogs shed their skin, normally it is a very quick process, as in a couple minutes usually. Then they eat it. With healthy frogs, their skin comes off usually as one piece, although sometimes it does get caught on their toes. If a frog is sick, then their skin will come off in little flakes. Is he or she eating? Do you have more than one frog?