on all 4 hooves right at and under the coronary band becomes white (he has white hooves) and slightly swollen and spungy feeling, soft and the worse I've found it the white band is about 1/2 wide. Doesnt seem lame, sore or anything really bothering him.
That is nothing to worry about. I liken it to the cuticles around my fingernails and if you keep your hands in water long enough, they will get mushy and appear swollen even though they are not.
It will shed off on its own. Different horses shed that skin at different rates and it also depends on the climate/environment the horse lives in.
My three Walkers had "cuticles" that were much wider than 1/2 inch. The Arab's were hardly noticeable. They all eat the same and they are all on the same pasture
Also out of 16 hooves on my farm, only three of them are white, hoof color doesn't play a role in this instance
That being said, ask your farrier about it on his next visit