The middle part of my tom. plant leaves have been turning yellow, i have cut them off the plant already, is there something i can do so this wouldn't happen again... the palnt is about 6 1/2 feet tall. I use compost teas, compost, mulch, and i water with a soaker hose in the mornings... Any ideas?

There are a large number of reasons why tomato leaves, or any plants leaves, turn yellow, first and foremost is that the plant no longer needs that leaf and is eliminating it rather than expending the energy needed to keep it around. Leaves are useful since they capture the sunlight and using that sunlight manufacture nutrients that feed the plant, using some nutrients in the process. If that leaf is not contributing nutrients to the plant the plant is not going to keep on feeding it.
Next would be that the leaf was injured, near the stem usually, somehow and it is not getting any nutrients from the plant.
Last would be a nutrient imbalance, insufficient in the soil, insufficient moisture levels so the soil nutrients are not moving up the plant, or the nutrients in that leaf were needed by the plant someplace else and were taken away from that leaf causing it to die off.