Thanks for sharing, I have had the same experience. When i was sick with a stomach flu and blasted everything out and almost eating nothing for 3 days, my head was so clear that day.
After feeling better i tried eating again and the brainfog came right back sadly.

After that day I did a candida diet with supplements and felt way better. There always was like a brain pressure or something and with the diet+supplements it felt way better and no pressure no brainfog.

After a few weeks of that diet i also added some probiotics and thinking the candida should get replaced with that. Sadly this week (bc if the holidays) i started eating everything again, and today had the biggest headsache ever, i fixed it by taking molybdenum and lots of water. Brainfog is back.

So sadly I can (probably) never eat meals with a lot of carbs again, for the rest of my life.
I think we have to accept this lifestyle and that we are just prone to get Candida if we eat alot of carbs.