There are many things that can cause overgrown or abnormal beak and nails in pet birds.
The three most common are:
1. Not having toys/perches to rub beaks or grind nails on
2. Nutritional problems (not enough vitamins in their food)
3. Mites
Any bird with an abnormal beak or overgrown nails should be checked by a veterinarian to ensure they are healthy, our vets can also trim the nails and overgrown beaks of birds of any size.