You are pushing the age limit for fixing it, but I think you still have a 100% chance. Don't wait any longer. Right now they are standing up, a little bit later they will be hanging outward. Down the road they can get injuries because they look like an airplane. Wrapping is not that hard, but it requires two persons to do it. Vet wrap at the horse in the feed store is very cheap, so there is not reason not to do it. Make sure that you first fold each wing under and wrap them. The final step is to wrap it all to the body. You do not want the duck to be able to stretch out the wing underneath the wrapping. Your duck, most likely, will manage to get out of the wrapping once or twice until you get it right with the wrapping. The wrapping can be taken off at night. Some keep it on 24 hours, but I have noticed no difference in recovery time with taking it off for the night. Your bird will be much happier in the long run, if you correct it now. 4 days of wrapping should do the trick. If not add a few more days.