I am so sorry to hear of your loss! It sounds like you've already got the same answers I would have given though, it would have been nice to have a fecal floatation done by a vet for parasites to see if that was the case. I would have thought impaction as well with the bottom being swollen, but it sounds like that has already been counted out as it was consistently pooping every day. Good luck with your next BD and don't let this one instance cause you to give up on yourself. There is so much misinformation out there for BD owners that it's absolutely absurd. That's why we're all here, so that we can ask questions from people who actually raise BD's and have had perhaps similar experiences and may know more about what's going on. The information that I've been given on this site has improved my BD's home life quite considerably, they are much happier and healthier dragons since we found this site.