I have seen this many many times but it only lasted a very short time then they straightened up. IF and this is a big IF it is a hereditary thing then I would be more concerned. I don't think this is something I would want to promote.??????? Oh yes, when I used to get them from the hybrids I was always happy.It may be that they are taking a while to settle. I'll send a PM after the holidays to the breeder I got them from if it continues. I can't image that he has this problem as he has sent out lots of chicks. I do like the super giant eggs for eating so all is not lost but I did want to hatch their eggs.
My other thoughts included climate differences. As Indiana weather much like your weather has snow and cold but a full week of snow does not really get down south where these chicks came from.
Jim
Good luck in your venture and I hope that it stops and never kicks up again. So far I think you are the only one having this problem or at least the only one saying anything.