We have a Landrace gilt that has developed red spots under its skin on its belly ears and shoulder. No bumps just dark red under the skin

I have a gilt that just started with a hacking cough and throwing up blood. She has been a great eater and all of a sudden it just started doing this. We are at a school barn, so a lot of others are hacking also. I gave it Baytril last night. What else can anyone recommend? The Vet cannot come out u...