You become intolerant to pretty much anything if you don’t eat it for long enough because your gut flora changes with your diet. This is one reason such a limited diet is unhealthy; weight loss is another. If you continue eating the problem food in small portions, it’s possible you’ll “readapt” to it like a vegetarian reintroducing meat. Coconut is very allergenic though, so maybe you are just sensitive to it. Either way I’d at least try to eat a wider range of vegetables and pull yourself out of ketosis – a potential source of stress.