what is causing my lower fan leaves to turn yellow? PICS

I have a single plant outdoors. She was started from seed in april and has been outdoors since day 1. She is in a 3gallon pot with fox farm happy frog. I use fox farm nutes and I ph the water to 6.8 - 6.3. She is about 4 weeks into flowering. She is starting to get yellow leaves on the bottom. I was wanting to know what might be causing this and what I can do to fix it? THESE PICS ARE NOT MY PLANT BUT THIS IS WHAT MY LOWER FAN LEAFS ON HER LOOK LIKE. any help or ideas would be great.

your 4 weeks into flowering?

nitrogen its normal, how do the leaves around the bud sites look

Twitch. said:

your 4 weeks into flowering?

nitrogen its normal, how do the leaves around the bud sites look

Click to expand...

they are nice and green. The yellow leaves are just on the bottom of the plant.