Marcobiotic diet is done in a progression. You gradually eat more brown rice and less of the other foods. (I am obviously not an expert on this diet, but know something about it.)

There was a professional basketball player back in the 1980's I think that developed osteoporosis from eating a macrobiotic diet. I can not remember his name.

No meat means no iron sources. All vegetarians need to check with their doctors to make sure they are getting enough iron. Vegetarian sources contain phytates which can interfere with mineral absorption.

Vegetarians need to know what minerals and vitamins their diet is lacking and they need to supplement those nutrients.

You are not getting enough zinc if you don't eat any animal protein. A zinc deficiency can cause fatigue. That is one possibility.

Not eating enough protein can make you deficient in sulfur. There is no recommend daily amount for sulfur. But some people do need more sulfur than others, because their body has a problem with sulfation. Sulfation is when the body converts sulfites into sulfates. Only sulfates can be excreted from the body. Sulfur is great for your hair, nails and skin. Some vegetarians have posted on other forums that their hair thinned on a vegan diet.

There are many nutrients that need to be looked when you eat a special diet. You can't just do a very limited diet and assume it will be OK. You really need to research this and maybe check your electrolytes from time to time.

Some people try to introduce animal protein into their diet and find that they will have some GI problems. Zinc is needed for HCL levels in your stomach. This can be one factor why vegans find it hard to introduce animal protein in the beginning. You really need professional guidence with this issue.