Hi, Just a guess but i would say you are correct. That it is probably excessive calcium.
I can create a list on many reason why not to have substrate with many species of chameleons, veileds being one of them. This just becomes a bacterial waste land even if you spot clean. Its just a matter of time when your chameleon will shoot and insect on the ground and pick up some substrate along with it. Two things can come of this if this goes on for a period of time. 1. The cham will become ill from injesting bacteria, its own feces and urine that was absorbed into the substrate 2. If the chameleon is not getting enough hydration. Substrate that is designed to absorb moisture (like Eco earth) will impact your kid. Prevent a possible bad situation and take the stuff out