Q.Discoloration of Leaf Veins in Chili Peppers
I noticed recently a dark brown discoloration on the underside of the leaves on some of my chili plants. The discoloration seems to be worse along the leaf veins. Not all leaves on plants are affected. There was a small outbreak of what looked like white fly, but I noticed it early and removed what I could see by hand and then sprayed the plants with soapy water. I’m wondering could the discoloration have been caused by the soapy water? If not, what do you think it might be and can you suggest what I should do next?

Certified GKH Gardening Expert
It may be scale, which is another kind of pest. Here is information on them: https://www.gardeningknowhow.com/plant-problems/pests/scale-bug-how-to-control-plant-scale.htm It may also have been caused by the chemicals in the soap sitting on the plant too long. When making insecticidal soaps, try to use a soap that is as basic as possible. Many people like to use Murphy's Soap for this reason.