How do you sterilize the tomato cages and do you still have disease? My plants suffer a late blight and not much I can do about it due to our close proximity to Humboldt Bay and cool night temperature.
I use a 100gl cattle trough filled with water and 2 packs of swimming pool shock, nothing will survive that level of chlorine. I also sterilize the stakes, tools, picking baskets etc. I deal with early (Southern) blight every year, once its in the soil other than fumigating you can’t get rid of it. I use several methods to keep it at bay for as long as possible, plastic mulch, pine straw mulch, pruning lower leaves and a strict spraying schedule with copper sulfate.
Late blight is a different animal altogether, it is airborne and can spread for miles in a single day. You might want to try some short season varieties like early girl, glacier or sub artic plenty to beat the cool Northwest nights.