Pseudomonas causes "reddish to purplish" brown spots that may cause the leaf to distort.
Xanthomonas causes small brown angular to circular spots with yellow halos.
Anthracnose causes small brown spots.
Botrytis causes large brown spots.
In addition the plant is prone to sun burning when the plant is exposed to too much hot sun. The sun burning causes irregular bleached dead areas on the leaves.