whats wrong with my sativas?

Do i need to just clip the yellow leaves i gave them one gallon of mg singles because it has a high N and a high P which the plants needed i just need sum advice.

No, don't clip them. If it has deficiencies it will start sucking the green out of the next leaf if you remove the yellow(-ing) leaves. Leave them on as long as possible. When they start hanging straight down or get mostly brown and crispy 'or' they come off with a gentle pull, you can remove them.