i dont know what i did..

Leon passed away recently. A week before it happened he was being his normal self, but as soon as i noticed that he wasn't drinking as much as he was, i took him to a chameleon vet in my area. I gave them his poop and pee from that day to see what was wrong. He was being very lethargic all of a sudden on our way to the vet and i was a crying mess because i knew that this was something bad. The vet said something was obviously wrong but the signs out side of him point that he should have been healthy. I took him outside all the time so he can bask, his crickets and everything was gut loaded, he had a cage that went up to my shoulder and he can come out whenever he wanted to to climb on the trees. I always made sure his temperatures were fine and I knew his stressed signs and colors and didn't bother him when he was. The vet said they will get the medicine and the results tomorrow so we went back home. Leon meant everything to me, he made me so happy and every time i came on here and saw someone said i should do something to make his life better, i added it and did it within a week or less. I wanted him to have the best longest life and i always thought that if he died young then it would be my fault and i would never forgive myself because i wasn't ready to take care of one. I still feel like that, but i tried so hard and i had a chameleon "expert" give me tips and i always called him whenever i was paranoid about him being sick or anything, he never was. The next morning, he was hanging by his tail, dying. My dad and my mom and all of us scrambled to get him some towels to lay on with the heat on him we were constantly misting and trying to feed him and give him water as we waited for the results, we even called early. I held him in my hands as he died. Im very young, and i'm sure there will be much harder moments in my life, but this so far has been the most difficult time of my life, he was my son, and i loved him so so much. The vet called an hour later and told us nothing was wrong and he should have made a full recovery, but that wasn't the case. My family told me it wasn't my fault, but i know it was something i did or didn't do that caused this. He was one the happiest chameleon ive ever seen, he was never his sad colors and loved to lay on me, i would try and put him on a tree or a plant but sometimes he would just want to relax on me like i was the tree, sometimes if i was taking pictures he would photobomb and climb on my camera. Caring for Leon was the best experience of my life and i will never forget him, some people said he was a runt or that he was small for a 2 year old, but he was so so strong. Writing this has made me cry and its so hard, but, It has been bothering me since this has happened. I want to know what could have happened because i thought not knowing would help me not feel so bad, but all i feel is guilt and confusion. If anyone has any ideas on what could have happened, please message me. Leon will forever be a big part of my life, and i just wanted the best for him, i'm so devastated i couldn't do that for him and now i just want closure on what i did wrong. This is one of the last videos of him. Theres this one too. Rest in peace Leon, I love you.