Well if you figure out the answer let me know.
My mom's border collie is shedding excessively now. She scratches or shakes and chunks of hair fly everywhere. It is really bad. She is on a good diet and we just put her on missing link this week. Hopefully the ML will work. But we have a theory why she all the sudden started to shed like this. It has gotten really cold here so we had to turn the furnace on, it is a gas furnace. And it is a dry heat and is drying everyone out including the other dogs, even my skin has been dry. Daisy started shedding when we turned the furnace on, before then she hardly ever shed. So we went out and got a humidifier to put moisture back in the air. Hopefully this will help too. The only other thing that seems to work for her shedding is some pills I get from the vet, I think they are called dermacaps and they are extra strength and they help alot. They only thing is they can be expensive. We didn't want to spend that much money but if everything we tried doesn't work we won't have a choice. So hopefully everything we try will work.
Sorry I can't really help you. I hope you can get it figured out soon, the shedding can be such a pain!!