What causes brown spots on the leaves of a tomato plant that otherwise looks dark green and healthy.
Brown Spots on Tomato Leaves
Certified GKH Gardening Expert
There are several things that could cause this, such as pests or some mild fungus or even possibly just water splashing dirt on the leaves, which then die in small spots due to lack of sun. I would treat the plant with neem oil. It affects both harmful pests and fungus and should take care of any possible harmful issues. Here is more information on neem oil: