We manufacture bath and massage products. We make a bath fizz that consists of: sodium bicarbonate (baking soda), citric acid, Epsom Salts (magnesium sulfate), Mango butter, coconut oil, polysorbate 80 and lemon and grapefruit essential oils and most notably CBD (Cannabidiol) and CBG (Cannabigerol) Isolate from Hemp. We have a problem in which there is purpling towards the middle of the clear tube. After a period of time, maybe 6 to 8 weeks, we begin to see a color shift from white to purple. We also had an issue where the metal top of the tube was rusting. We resolved this recently by replacing the metal top with a rubber top.
Could there be a chemical reaction happening between ingredients that is causing the discoloring of the product after a period of time? Why would the reaction happen in the middle of the tube? Because if light or heat is a catalyst, it wouldn't affect the middle of the tube but rather more evenly in the container. Uploading photos to illustrate. Thanks in advance for any chemistry advice!