In all the videos I see about starting to make Kombucha, they all seem to say (roughly) "You want to use 'original' Kombucha, and not flavored. If you use the flavored stuff, you are going to have problems." But I cannot find anywhere an explanation of what these problems are. I get the feeling that people just repeat what they have heard and don't even know why they are saying it beyond that.
For additional context: I made a scoby from a 1.4L bottle (the huge one) of GT's Trilogy Kombucha. They don't call it flavored, but it is red instead of... yellow/tan(?). I'm wondering what kind of problems I should be looking for.