I'm growing some organic tomatoes (mostly cherries), and noticed the other day that there were small purple spots forming on the leaves, and they are gradually turning purple and curling inwards. It doesn't look super fungal to me, and it has been humid but not super wet (though it just rained before I noticed the spots). I've been watering with a soaker hose, so trying to keep moisture off of the leaves. Based on my plant-webmd searching, I have thus far considered the following:
- Fungal/Bacterial spot (but doesn't seem to be a yellow halo around the spots, leaves seem otherwise intact)
- Phosphate deficiency (but hasn't been cold, had added a bit of manure to the soil when planted a couple weeks ago, and also the veins are still green).
- Tomato purple leaf disorder (came up in my google searches but seems obscure and only article I can find on it is from Florida, while I am in Southern Ontario..)