My 22 months LO has not been gaining weight since she was 18 months. Is that normal for the weight to be stagnant?

Yes of course dear. They are growing older. And will slow down through the growing process. Ensure that they are eating and drinking. If nothing comes up, all is well. Chill out

yes it's perfectly normal as they are getting more active and running around and constantly burning calories. Just feed them well with sufficient nutrients and vitamins will do.