Mema, I think if I get what you are saying you are talking about the smuttiness that appears in alot of laced wyandottes? or are you talking about the actual feather quality of the birds?
If you are referring to the smutiness it has to be bred out and it is really one of the hardest things about any variety of laced wyanodottes is keeping full lacing on the breast while at the same time cleaning up the lacing on the tails. Better quality breeding stock(ie show birds) have been selected for very bright and clean lacing.
If you are talking about feather quality, some of it can be attributed to diet but it is also something that varies depending on the quality of your stock. Cochins are a real good example of that. If you buy hatchery cochins they look like great birds but people will wonder why they dont look the same as show stock. Look at their individual feather. You will see a great difference in the size and quality of each feather that really makes the show stock has a much wider, fluffier feather. To a certain degree I would say this is the case in alot of other breeds also. Of course all of this is just my opinion from my observances of raising both hatchery and show stock in the last 30 years.