Discoloured toenails can be more than just unsightly. They may signal an underlying medical condition problem, physical damage or an infection that needs to be treated before your nails can return to their normal appearance.
Wearing shoes that fit properly and allow you to wiggle your toes can help your toenails from thickening as a result of pressure.
Avoiding nail polish that is dark in colour and applying a base coat to your nails can reduce staining of the nails.
If you believe your nails have a fungal infection, you should seek advice from your GP or Podiatrist about treatments to tackle it.
It's also worth noting that nails become less shiny with age. This is because the surface tends to lose its smoothness, making them less able to reflect light.