Your plant is showing the symptoms of overwatering. For many months I experienced the same problems with all of my plants and I could not find a cure. Even with proper elevation, drainage and air flow, I still had plants suffering and dying from overwatering. I finally found that the problem itself was the soil. Since chameleon enclosures receive lots of water, it can often damage the plant. This is way a custom type of soil is a must. Regular soil contains to much clay, which retains water. Adding sand to the mixture allows for much easier drainage and also protects the plant from "sitting" in water. Right now I have been using a half coconut husk and half play sand combination in all my pots. It has been several months and I have still not had one death/problem. For details and proof of it's success, check out my blog
https://www.chameleonforums.com/blogs/cushcameleon/131-custom-plant-soils.html#comment235. I am sure it will help your problem.