sorry to hear that rick, wish i was nearee to have a look! i had paramoxy last year in my stock birds, very similiar symptoms to paratyphoid! killed the lot, was heart and pocket wrenching! bought a couple of dodgy stock birds!!
coild be a number of things though! has it started since you started breeding? what have you gave them different? have they been in the garden? fielding? could it be poisoning? like bruno says only real way is autopsy, wont be cheap, but wont be cheap treating blindly either, then end up at square one again,
hope you get it sorted out, i know what your going through,
let me know if ya want any ybs or owt mate :-/