I'm sorry to hear you have another sick chicken.
Is vet care possible?
Photos may be helpful.
Mycoplasma can be transferred on dust, dander, clothes, bird-to-bird and from wild bird flocks as well.
Talk to your vet about vaccination. I do believe you may be able to order a vaccine for MG, but you would need the correct equipment to administer it-I believe it is sprayed and administered in healthy birds 9wks or older, but there are probably other vaccines too - I really don't know, I don't vaccinate.
There is no way to know for sure if the Polish and now this sick bird is related or not. Only necropsy/testing could have given you that information.
IF you believe your chicken is sick from MG, you can try Tylan50 to see if that helps. Dosage is .25ml per pound of weight given orally 3 times a day for 5 days. It's important to also flush the eye several times a day with saline. You can also apply Terramycin eye ointment 2X a day.
Bubbly eye/swollen face would be indicative of MG, but there are other respiratory diseases that can start similar. Also infection of the eye from another source (dirt/feces in the eye), an injury (look for a small scab), molds and ammonia from poor ventilation and excess feces in coops should also be looked at.
Here's a link to your state lab - they may be able to take some swabs to find out what you are dealing with.
https://tvmdl.tamu.edu/