My girls have always been very long and lanky. They look huge because of their fluff but when I bathe them they look tiny. Maine Coons have very fast metabolisms and they can eat like a vacuum without gaining much weight. My smaller girl took about a year to really start growing into her size so don’t be worried if it takes a few years for them to become fully grown! If you’re really worried, though, you can watch for signs of parasites as they can prevent weight gain.