Please help. Sick chicks

[Chickenman mike]

I have 12 Cornish rocks that I am raising in a tractor. They are starting to gasp and make a funny chirping sound. Two have died. I started moving the tractor more often, twice a day, to keep clean ground under them.
I have a free ranging flock of giants that are perfectly healthy. So I don't think the cr's caught something off the ground.
Any one have any thoughts?

 

[Mamabrinkles]

Cornish rocks have a reputation of having an above average mortality rate. It seems that they can grow too fast for their hearts to keep up. I have read that the mortality rate is greatly reduced by feeding fermented food. Best of luck to you!