Our serums vary slightly from batch to batch in color, scent, and consistency because the bulk natural ingredients that we use (particularly plant extracts) vary a bit depending on batch and season. A pale yellow, cloudy serum is perfectly normal for our Vitamin C Serum due to the chamomile, clary sage, and konjac used in the formulation.
We use a very stable form of vitamin C called sodium ascorbyl phosphate (SAP) that does not oxidize easily even when exposed to heat for brief periods of time (such as during shipping). A bottle of our Vitamin C Serum has a 30-month shelf life when unopened. But, once opened, it should be used within 4-6 months for maximum efficacy.