My nails never seem to grow and they always chip! How can I get stronger and healthier nails?

i already take vitamins everyday what else can i do?My nails never seem to grow and they always chip! How can I get stronger and healthier nails?
Drink lots of milk oh and there is a special nail polish thing that helps make your nails stronger and healthier :)My nails never seem to grow and they always chip! How can I get stronger and healthier nails?
there's many nail polish brands on the market which claim to make your nails stronger.