Weight for Welsh Harlequins should be around 5 to 5 1/2 lbs, a young bird should be right around 4 1/2 to 5 lbs by the time they are in their first set of breeding plumage.
From looking at your pictures, your birds will be bigger than that. You have one bird that is pied, (the one with the white on the face in the 1st picture below the muscovies. True welsh harlequins are never pied birds, but often the stock from Metzer come out that way. That being said all of those birds that I've seen in person end up larger and closer to 6-7 lbs. Of course from time to time we even have larger bodied birds hatched from our show breeders and (if males) are always culled from the property.