I’d start soaking each ones feet in some warm Epsom salt water pick up some clear iodine and after soaking use a q tip and put the iodine over all the places that look like bumble. If there is a scab then keep soaking and using the iodine until you can take you finger nail and gently pull the scab off it might take a week or less but don’t get into a hurry. And don’t let them drink the Epsom salt water it’s also a laxative. Once you get the scab off there will most likely be a plug that needs to come out but before you start post pics. When I soak I use a bucket and put both feet in hold onto the duck and let them soak at least 5 min or longer depending on the duck. That way they can’t get to the E.S. water.