My boa is hiding and breathing with her mouth open. What's wrong?

Check her mouth for foreign bodies, injury or infection if she allows. Monitor for persistent or worsening symptoms and have her examined by your vet or a vet experienced in treating reptiles if necessary. If she is behaving and eating normally otherwise, it may be simply something unique she does.

It sounds like she either is trying to regurgitate a meal or she has a respiratory infection. When was she last fed? How large was the prey? How often do you feed her? Do you hear any wheezing? Any bubbles coming out of the nose or mouth? I don't really have enough information here to be helpful. The yellowing of the scales appears to be mild scale rot. You can try treating her at home with dilute betadine solution (1 part betadine to 10 parts water). If she has yellow scales all over her body you can soak her in a betadine solution bath for 20 minutes TWICE a day every day until the infection clears up. If it is just the location in the photo you can just apply the dilute betadine directly to those areas with a cotton swab. The betadine solution should be 10% betadine and the water should be lukewarm (80-85°F). After bathing, rinse the snake off and apply a topical antibiotic ointment (something like Neosporin will work fine). If the infection doesn't get better or even worsens, discontinue the betadine baths and seek professional help immediately. If you would like to post again with more information or opt for a private consult we may be able to help you better. Hope this helps. Best wishes.

She may be "gaping". This behavior is typically in response to stress or a threat. Monitor for lethargy, wheezing or a clicking/popping sound whilenbreatuing. These symptoms, along with the gaping, may indicate a developing respiratory infection. You would need to have her physically examined by your veterinarian or a vet experienced in treating reptiles for confirmation and treatment.

Bowie looks as if he is going into a shed. If you're saying he has recently shed, the blue eyes may indicate infection or other condition. The wheezing is concerning since it may indicate a respiratory infection (RI). Ideally, Bowie should be physically examined by your veterinarian or a vet experienced in treating reptiles. If a RI is diagnosed, antibiotics can be administered or dispensed.

Chong needs to be seen by an experienced herp veterinarian as soon as possible. By your description, he may have a respiratory infection. The clicking and gasping may indicate advanced infection which can be stressful causing the posturing. It may also be neurological in nature. For this reason, an exam is strongly recommended.

Upper respiratory infection (URI) in snakes takes a very long time to resolve and it is not likely to resolve without antibiotics. You really need to get him to a vet as soon as they can get you an appointment. There appears to be multiple vet hospitals in your area that will examine/treat reptiles. I suggest you continue to call around. One thing you can do right away is go over all of your husbandry. A URI most often happens because the snake became too cold. There is really not much else you can do at home. The antibiotics are really what is needed. ( https://www.reptifiles.com/red-tailed-boa-care/sick-boa/respiratory-infection/ )

Have her examined by your veterinarian or an experienced herp vet. The lump may be a temporary build up of fluid that collects and drains when she changes positions. This can indicate respiratory infection or cardiac disease. Monitor for difficulty or noisy breathing, especially clicking or wheezing. Limit handling to reduce stress until she sees the vet.