Multiple vendors, such as vapor4life (v4l) resell China-sourced eliquids. I've heard they are produced in bulk, factory, clean, settings.
In the US, I would have no concern with eliquids produced by any of the well-known artisan vendors, places like Backwoods Brew and Kickbass Vapor. They've been around long enough, have built up solid, consistent, reputations for quality eliquids. Whether you like a particular eliquid is a matter of personal taste, but I wouldn't fear bad standards relative to cleanliness or mixing.
Tightness could be over-vaping, or a sensitivity, whether to PG, VG, or a particular flavoring. Some people have to go to 0 PG, all organic flavorings. Others actually have the opposite, need 0 VG, do well with classic Dekang Chinese eliquids.
Concerning DIY, look here:
DIY E-Liquid
Multiple forum areas have DIY recipes threads or subforums, to get examples. For instance,
http://www.e-cigarette-forum.com/forum/pay-forward-pif/110029-diy-recipes.html