Hello,
your room temperature is about correct, however please adjust humidity and storage temperature. I've attached some image from my book CCG on the correct temperature and humidity, hope it will help.
Now to answer what is the real issue of your coating tempered chocolate that separates and crumbles from the ganache (center) is as follow:
- Missing of fats in your ganache (we talk here about butter)
- Missing of inverted sugar
- Bad emulsion of your ganache (use spatula when you mix ganache at first, then when you add butter at 35-36C, mix it with blender) - dont use whisk its a comment mistake
Note: don't use 70% dark chocolate to coat centers of ganache, its not recommended, better use around 55% Dark
I hope I was of a help, let me know if you have other inquiries.
Merci
