Deedles, try to save the meat on them if you can and as quickly as you can. Could be you can salvage some of the meat off them if you hurry.
CX birds that are not fed free choice feed all day and not confined to a pen/run/tractor will grow slower and that's the expected and desired response. Getting a meat bird to butcher size is not a race...as long as they get big enough before they are too old to have tender meat still (past 5-6 mo.), then you are doing the right thing. The point of raising them free range and on restricted feed is to slow the growth down so the bird stays healthier and grows at a more normal rate.
Anyone believing that they must be X wt. by X time or you're doing it wrong are those who are trying to raise meat birds like they do commercially....and those folks just miss the point of raising them at home. If you get the same birds as commercial growers and then raise them like commercial growers do, then you'll have what the commercial growers produce.....and you could save yourself a lot of money and time by just going to the store and buying it from the commercial grower.
You hadn't done anything wrong except listen to the accepted wisdom about how big your birds should be by a certain time...if you do this again, just ignore that kind of noise. I raised mine on the same thing....fermented layer ration and free range and they grew slower....and I knew they would and that was what I expected and wanted to happen....but they did indeed grow and were of good butcher weights by 10 wks instead of 8. The difference being not a one died due to ill health, no leg problems, and were completely mobile over 3 acres right up to the day they were processed.