Yellow leaves on mature tomato plant

Question

One of my potted tomato plants is doing well, and the other is scrawny and pale yellow is replacing the green. These plants are about 3 months old. I used a good fertilizer in the beginning. They both have blooms that are healthy looking. What can be the cause of the yellow leaves and lack of thriving?

Answer 1

This article should help: https://www.gardeningknowhow.com/edible/vegetables/tomato/yellow-tomato-leaves.htm