well... when i make e-liquid for my friends and family there liquid always turns bright yellow and becomes harsh after 1-4 weeks of vaping/steeping it? there nic levels are always between 10-18..this never happens to the ones i have made for myself at 6mg and i always store them away in dark cupboards but my friends and family say they do aswell? so why is mine not going bright yellow and harsh like theres is? just goes a slight tinge of brown and is never harsh even after 2-4 weeks steeping or use? vg/pg ratio is 50/50 and stored in amber glass bottles or HDPE bottles?