Congratulations on finding something that works for you! I believe one of the most important lifelessons we can take is that we're all unique and have unique body chemistry... so the whole notion that there is some kind of "one size fits all" when it comes to diet is basically so much BS.

At the recommendation and (almost) insistence of a couple of (almost) militant vegan friends back when I was 20-something, I managed to go vegan/vegetarian for about six months. I gave up the experiment at that point for health reasons; pretty severe anemia, really bad acne, skin pallor, achy joints, muscle weakness, acid reflux so bad I would sometimes sit for 20 minutes in a semi-fetal position, lack of energy and frequent headaches (which I had never had before) and went back to meat eating.

Now, in all fairness, I was eating pretty much the exact same thing as my buddy Kevin who was quite healthy... not exemplary, by any means, but "quite healthy." I just wasn't.

After about three weeks of eating mostly red meat and salmon, I was back to my former health... which was actually really good.

In retrospect, I think some of this might be genetic... being from upper Scandinavia, it's a part of the world where I have a genetic inheritance for surviving in an environment where a plant based diet would only have been historically feasible for about six months a year, and survival/health would (for my ancestors) have been dependent on access to fish and meat. My experience has been that people genetically from hit climate zones are more likely to thrive on plant based diets.

Your fair skin (in spite of living in the tropics) and reddish hair also suggest a northern genetic heritage, so that fits the pattern, too.