I'll try to be constructive before the less kind members show up.
The first thing you can do to help us help you is give us a summary of your grow. What kind of soil are you using, what kind of nutrients (how much, how often), how are you watering (how often), what kind of light are you using, temperature and humidity of your grow space....
Second thing to do is clean your space. Dirt and shit all over your space is creating an opportunity for pathogens and bugs.
Looks like you are overwatering most likely, and it appears there are problems with uptake of nutrients possibly related to root issues due to watering practices, or perhaps because of pH issues.
There is a lot that can be improved but we need more info.
