I am an amateur bodybuilder and therefore keep up to date with the latest nutritional research.So this advise is gleaned from the scientists that actually do the research.
1. Soda - There are only 2 liquids that the human animal is meant to drink,milk and water.Soda drinks are usually acidic and contain artificial sweeteners that have been reported to be not only a gastric irritant but also neurotoxic even carcinogenic.
2.Potatoes - The problem with any heated carbohydrate(potatoes,bread,pasta,rice and Popcorn)is that it can raise blood-sugar levels faster than pure glucose,the body prefers a trickle feed nutrient supply,but Candida and Cancer love that Sugar rush.But this rapid absorption can be slowed by fat and fibre,so it's skins on with butter and/or cheese,if your watching the calories have a smaller potatoe.
3.Soup - Homemade soup is a very option as long as you follow a good traditional recipe,modern commercial brands are often packed full of Sugar and salt.It's an old chefs trick to fool the brain into thinking it's a higher quality product.
All your symptoms are the ones that are claimed for Candida. I myself have suffered from Brain Fog for a few years now and 2 days ago went on a low carb diet,the fog has reduced by about 50%.Of course 2 days is too soon to make a definitive judgement,but it's the first light in this long dark tunnel that I've ever seen.
Hope this helps and Good Luck.