My pet ball python (i’d had him for about 3 months now) was fine last night. I got him from a reptile expo back in december from a breeder. I cleaned his cage with a vinegar and water solution and put him back in his cage along with a branch from an evergreen tree i’d found that i thought he may want to climb on. I remember reading back in december that those branches could be harmful but i figured since there was no scent on it anymore he would be fine. I woke up this morning and he was dead, and I have no idea why. Humidity levels were fine, temperatures were fine, and he’d just eaten on wednesday. He used to be uninterested in feeding until i fed him live for the first time last week. I’m so afraid that I killed him but i did so much research and he seemed so healthy last night. I loved him very much so any advice on what may have happened would be greatly appreciated, thank you.
I'm sorry to hear about your snake.
It is possible that the evergreen branch still posed a threat. I work as a reptile keeper in a zoo, and we as a rule will not use any evergreen regardless of its age. It's also possible that the branch had been contaminated by chemicals, especially if it came from a farm area.
Other possibilities: Lack of adequate temperature gradient (ball pythons can be quite sensitive in my experience), impaction from substrate ingestion, difficulties shedding, food poisoning or illness.
As I'm sure you are aware, another possibility is that your python simply had a genetic defect which you could not have known about. These are sadly quite common in mass bred snakes.
If you are able to, your best option is to ask a vet to perform a necropsy for a small fee. You aren't guaranteed an answer, but you will be able to conclusively rule out several possibilities.
First, sorry about your snake. I tend to agree with Chameleonbones, but I'm going to expand a bit.
It sounds like the most likely cause was evergreen branch, though I am surprised it happened so quickly. That seems to be the biggest change/unknown and the timing is a little much to be just coincidence (though of course there could still be unknowns like genetic defects, food poisoning, etc.).
You said "evergreen" and though this could be a several different types of trees, one of the most common types is Pine. Pine and Cedar (and probably others that are closely related) have oils that can be very toxic to snakes and should not be used in the enclosure. Even if you were to use Pine to build a tank, you would need to seal/paint the wood to ensure the animal could not come into contact with these oils.
Because the potential risk is so high, I would recommend never using any type of evergreen anything in a reptile enclosure. If you want to provide your snake some things to climb on, please either purchase branches/decorations from a proper vendor, or buy some PVC and make your own. I know paying $15+ for a stick can seem ridiculous, but introducing so many unknowns and possible dangers to your pet just isn't worth it.