How old are they now? You absolutely must fix this issue right away or they will not be able to walk properly as adults, and maybe end up with very deformed legs. These problems are usually very easily fixed if done as soon as possible and while they are very young. Can you post pics of their legs?
What have you been using to make the hobbles/braces? I use bandaging tape so that it sticks well enough to their legs (can't be pulled off by them if kept dry), but is also easy enough to remove a few days later without causing damage to their skin. You can also try vet wrap, but in my experience it doesn't stay on as well and they just slip it off sometimes.
Here is the Poultry Podiatry site that Amiga mentioned. It is great for showing how to fix various leg issues in ducks and other poultry:
Also, like Amiga said, it is very important to have them on a surface that is not slippery. Newspaper or something like that is not appropriate and will cause these kinds of leg issues. I keep ducklings on old towels for the first few days of life (until they are eating well and know what food is), then I switch to wood shavings.
Edited by Orca5094 - 2/18/16 at 3:18am