Tomato leaves turn yellow due to lack of water, sunburn, too much or too little fertilizer, or disease. Are you noticing just the lower leaves turning yellow or the entire plant? Lower leaves could mean too much water, leaves with brown tips could be sunburn or too much plant food, and yellow on the entire plant is a sign of disease or root damage. As for broccoli, it will bolt or go to seed as soon as the weather gets hot. You can replant now for a second crop in the fall. Keep growing, Marianne Binetti