Rich hit it exactly. The main problem is that these "curtus" group species (bloods and ST's) are very susceptible to low humidity levels and subsequent lung tissue irritation. This on top of the fact, that like Rich was saying, wild caughts stress easily which only further compounds the situation. If your humidity level was around 50% I would say that was too low for "curtus" group pythons. Usually anything below 60% for an extended period is going to be a problem for them. I try to keep my levels around 65 to 70% for my brongersmai.
On another related and important issue, it is possible that your humidity was even lower than you thought. Lower price humidity gauges are notorious for being inaccurate. Unless you are willing to spend 150 to 200 dollars for a NIST traceable with a certificate, you can never be sure if your hygrometer is reading accurately. However, you can test your own quite easily to see if it is reading properly, and here is the procedure:
1. Place a teaspoon of salt in a bottle cap or small cup and dampen it with a few drops of water (without dissolving it) to make it the consistency of wet sand.
2. Carefully place the wet salt and the hygrometer inside a see-through container and close tightly. Don't allow any of the salt to directly contact the hygrometer. You can use a zip lock bag provided it seals good and you leave some air inside as well, or a plastic food storage container as long as it seals airtight.
3. Let it sit for at least 8 hours at room temperature and note the reading on the hygrometer without opening the container. It should read 75%, and the difference is how much your hygrometer is off.
4. If it does have an adjustment screw or other adjustment device, adjust to 75%, through a small hole made in the bag if necessary.
I have an expensive certified dial hygrometer I purchased many years ago and have checked it periodically using this method, and it does appear to be a very accurate way to check humidity gauges.
Kelly