Yes, it contains Vc, it will be oxidized in contact with air, producing spots, the bottle generally have desiccant, every time you eat the bottle cap screwed tightly, insist on eating, it will not happen, but also may be related to the place where you store it, there are spots on the do not eat it, the front, if you eat it, it does not matter.

Next time you store it, just pay attention to it and try to put it in a dry place.