Powdery Mildew (I think)
I am growing 3 tomato plants in 3 containers; the plants look healthy except for brown leaves on several stems on each plant. I also saw a white powder looking substance on the tops of some leaves that I assumed was powdery mildew. Following a solution I found on the internet, I washed off the plants and then sprayed a solution of baking soda, vegetable oil and castille soap on the tops and bottoms of all the leaves. Is there anything else I should do? Should I cut off and discard any stems with brown leaves with pruning shears?