Could this be caused by sodium? i recently changed my diet to veganism and find the foods and some meals are higher in sodium. when i had rice cakes recently it became worse. same when i had marmite on a slice of vegan bread

Probably not: If you did not grow up in a vegan family one of your main risks of adopting that lifestyle is vitamin deficiency Lack of B12 found in meats among other things can cause a variety of problems including some mentioned. I would visit your doc who may check levels. I would also consult a clinical nutritionist to learn how to get your needed nutrients as a vegan.

Mouth sore, cracking: May be vitamin deficiency , can be due to deficiency of B Vitamins, Zinc . The white patches may be thrush /candida due to lack of vitamins, relative immunosupression. May need Nystatin . Would also check blood count , and for strep. F/u /w/ MD https://www.livestrong.com/article/409132-the-vitamin-deficiency-that-causes-the-corners-of-the-mouth-to-crack/