Question about texture of coat and overall color

I have two cavs -- a 15 month old tri-color and a 7 month old blenheim. They have both been neutered. I'm not really one who is believes that neutering them changed the texture of their coats, although I am wondering if there is a cause for the change or if it is normal.

The tri-color has more of a wooly, cottony coat on top (back area/bottom by tail). His fur on his ears and his "skirt" is very silky and soft. I've also noticed that on his back his fur is a slightly different shade than the rest of his fur -- the black has a tint of burgundy in it. So it has an almost reddish hue. He has a lot of black in him, more than white.

The blenheim coat is a little coarse -- when I give her a bath, her fur almost looks like it has been crimped! Ha. Are a lot of cavs fur like this after a bath?

Is this pretty normal? Could a change of diet help their fur to be more silky, shiny, and soft? Right now they are on California Natural and I supplement their diet with grizzly salmon oil. Any advice is appreciated! Thanks.

I have three sets of littermates here. EVERY one that is neutered has a different coat than their siblings. I have found that the intact dogs coat is easier to manage than a neutered coat. The wooly coat can be managed with the right tools. There is a mars 'ear' brush that will take the woolies out and so will a comb with a rubberband weaved through it.
Intact dogs blow their coats, neutered dogs seem to hold onto it and it gets crimpy or wooley. jmo

I've been wanting to post a related question, so I'll add it here. Daisy's feathering on her sides seems to start way up higher on her sides/back than other Cavaliers. About 3 inches away from her spine, really long hair starts (like literally 8-10 inches long.) And unfortunately, right where the short hair on her back ends and the long feathering starts, the color of her Blenheim patches is much, much lighter. It makes her look like she is bleached out in the sun. I've even had people comment how much they like the color of her blenheim patches on her back. Of course the unspoken comment is that they don't like the color of the patches with the longer hair which are faded looking. (I don't either!)

I used to think it was because I was using Chris Christensen's White on White and it was causing that longer, older hair to fade, but I haven't used that in about a year, and I've seen no difference. One lady at a Cavalier show said Daisy's hair needs to be stripped, so I've been Furminating her periodically. Again, little or no difference. If you pull back the long hairs, you can see that they are markedly lighter than the blenheim patches on the top of her back, beginning right at their roots. There are days when I'm tempted to cut off her side feathers so they will start about 1/2 to 3/4 of the way down her sides, thus getting rid of most of the blenheim colored feathering. But I'm really scared that then that shorter hair will stick straight out sideways. Or that she will have Karlin's hated "combover" look!

Any suggestions or experience with this type of problem?