Having come across and heard of several excessively growing beaks & nails recently, including Scissor beak thought i would post this for the benefits of the carers of these birdies.
This is taken out of my Holistic 'bible' & i have actually used this treatment with excellent results. The Milk Thistle liquid i use is alcohol free by Natures Answer. Add 4-5 drops to water daily for up to 4 weeks then once weekly there after. .....

Beaks that grow long and need repeated trimming are a symptom of disease . The disease is often associated with the liver. Many of these birds also have weak thyroids as well as liver disease. The birds diet needs to include Higher high quality proteins, and feeding egg yolks can be helpful.

Herbs that can help these problems include Milk Thistle which detoxifies the liver and in turn reduces the speed of growth in the beak & nails. For more severe cases using products containing herbs that help the body metabolize fats can help. These products are called ' lipotrophics' which remove the fats from the liver. These include Choline and  Methionine.

Written by Shaz.