Hello Persephone and welcome to this list!
It seems I've written this several times already, but when I first started and those times that I've gone back on the diet after a prolonged period of cheating, I get a migraine attack followed by 1 or 2 days of lighter headaches. That's it for me, so I really hope yor "brain-fog" is clearing up now. Just make sure you drink enough, and get enough potassium and magnesium in your food. You might even want to consider supplementing those minerals for some time.
Best;
Erik F.
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