Thanks everyone! Right now I'm putting them onto a local diet dog food. It is designed by a local vet/dog nutritionalist? so hopefully it should get their weight down a bit more!

I'm lucky that I have a fantastic landlord who lives on the 2 1/2 acres next to me and has 5 GSD's, one with cruciate ligament injury. He does work for a lady at the SPCA and she gives him food at cost. Anyway, he said he'll buy for us too! He's sooo nice!!!!