excessive shedding

I have 2 Chesapeake Retrievers. This is a non shedding breed and my
dogs are 7 years old. For 4 years they have been shedding excessively.
One of them was treated for a bacterial skin infection: she lost her
coat completely, but then it came back beautifully thick and shiny.
They were tested for allergies and are allergic to everything outdoors.

They are on a potato and rabbit diet for years now, but nothing seems
to quiet down the excessive shedding. Everytime I brush them I can fill

up a bag with fine fur. They have the curly coats of Chessies but not
the thick coat you would expect. The vet believes this is genetic
problem, probably with the whole litter, but the breeder denies anyone
else has reported this to her or asked for her suggestions. I wonder if

anyone can suggest any supplements. I already add Omega 3-6 and Hemp
Seed Oil., I am thinking Safflower Oil might work, and maybe the raw
egg. They are energetic and wonderful dogs, but for non shedding dogs,
you would think they were Goldens.. Help.... Linda