Yellowing of leaves

Nitrogen is stored in the lower leaves. When plants mature and run low of N in the soil the plants will take N from the bottom leaves and move it up the plant to the newst growing points. This is normal- but I would add a little more feed since you still have a while to go.

Yes this is normal it just means they aren’t getting enough nutrient but the top of the plant is

Yes mate, its completely normal as the plant uses the rest of the N stored in those leaves.