If the lower leaves on the tomato
plants are all that is affected, just remove them. They are an annual
plant anyway and you're not
growing them for the leaves. Leaf miner tend to attack young growth and leave a silvery trail under the skin of the leaf. Older leaves which were affected will look curled and misshapen but they will be otherwise OK., The larvae responsible will leave the leaf and then the leaf gets curled up as it ages. Older leaves are susceptible to fungal diseases such as blight and wilts. This could be the yellowing. It's really just a natural part of the aging process with tomatoes. These lower, yellowing leaves should be removed and the
plants should not be watered overhead as this helps the spread of these diseases.
SO, flood the soil at ground level, in the morning is best so the area is dry at night and remove affected growth as it starts to yellow. Dispose of these leaves in the rubbish, don't compost them. Mulching will help to retain moisture and also help prevent water splashing up onto the leaves during rain.