Grains in general are pretty nutritionally void, except for calories. Any micronutrients in them were put there after processing. Many grains contain anti-nutrients which means they actually interfere with the body's processing of nutrients from other foods. And then there is wheat gluten and gliadin which not only produce allergies in some people, seem to produce long term degenerative disease in nearly everyone. If you take any time to look at the research, you will see that just about every degenerative disease we have is an autoimmune condition and wheat is the primary instigator of autoimmune diseases because of the action is has in our intestines, even in those of us who are not allergic. Arthritis, alzheimer's, diabetes, heart disease etc. are all autoimmune conditions. Why does the body attack itself? Foreign proteins are able to move through the intestinal wall into our blood stream thanks to the proteins in wheat. Add in the omega 6 oils and you have a deadly cocktail unfit for human consumption. Bird seed and bird seed extract.
I would say that a few corn tortillas now and then are not going to kill you, so long as you're sure they've been properly nixtamalized (prepared with lime, not the fruit but the chemical) and don't contain genetically engineered corn which they know is not fit for human consumption but sneaks into the food supply anyway. Rice is a safe bet. Don't base your diet on grains in general. They should be no more than a small side order that you have infrequently.
Female, 5'3", 49, Starting weight: 163lbs. Current weight: 135 (more or less).
I can squat 180lbs, press 72.5lbs and deadlift 185lbs