Lower protein Feed to prevent Angle Wing ?

Last year when I was raising Ducks at about 5 or 6 weeks they started getting Angel Wing and I was feeding them 15 percent protein chicken layer pellets.    I am at 5 weeks this year and want to reduce the protein
for a few weeks while their wings grow  and would like to mix something with my layer pellets to reduce the
protein content.   I was thinking of just mixing in cracked corn 50/50.    Does anyone that knows more about it
think that that would work for the next 2 or 3 weeks that they are susceptiple to the angel wing ?