Welcome to ooshi. With just that little bit of info it will be hard to diagnose what is happening. I'll leave a link below for you to read through. Hopefully it will help you figure out where you are going wrong.
How old is your plant from when you 1st saw it sprout?
What kind of light do you have it under?
How far away is the light from the seedling?
How often are you watering your plant?
Do you let the container dry out completely or are you adding a little water each day?
Is your plant in soil? Hydro?
What size container is your plant in?
Are you watering with tap water, distilled water or RO water?
Are you testing the PH level of the water you are giving the plant?
What is the temperature of the growing space?
What is the relative humidity of the growing space?
Are you exhausting the grow area or is it in an open area?
As you can see, without at least a little basic information you asking what is wrong with your plant would be much like me asking you, I have a stomach ache, what caused it?