So I've been mixing my own liquid, and been really happy with the results overall, but I started noticing that my liquids are getting darker after a few days. My supplies are all in amber bottles, and they seem fine. But when I mix up a small batch of flavored liquid (usually about 10 or 15ml) I put it into a small clear plastic dropper bottle. The liquid looks clear on the first day - and after a few days it gets an orange like tint to it. Since I noticed I've been keeping an eye on it, and have noticed that it's getting darker still. I'm guessing it has something to do with exposure to sunlight. But mainly I'm wondering is this something I should be concerned with at all? Is this just an effect of the flavoring, or is it an indicator of impurities in the liquid? Any thoughts?