I use an RBA with a sub ohm coil and I have found that some juices create a carbon like buildup on my coil. Some are worse then others, like Zues juice for example is the worst. With any of the Zues juice line I have to clean this "carbon" EVERY tank full as it becomes at least 1mm thick and the coil performance suffers severely. On other juices I might have to clean it like every 5 tanks, but with some vendors I never get any of this buildup. Any idea what causes this???