Yes a vet and or testing is always ideal. I know it's not always possible.It would be best to actually have a diagnosis, rather than guessing what's wrong. Some things are treatable and will go away, and some things are forever, and it's best to know. Call your state poultry lab if necessary, and find out what your best plan will be, moving forward. Meanwhile, don't add birds or move any to any other flock, and that includes eggs. Mary
If no vet is available and you can try and narrow it down for testing.
I don't have access to a chicken vet and testing can be an expensive stab in the dark. Trying to give as much info as I can.