Hi, all. Im new to gardening and this site. I built my firs garden this off year and was off to a good start until vine borers got my spaghetti squash, powdery mildew plagues my zukes and now my tomatoes! The leaves seem to be yellowing then dying from the bottom up 1 stem at a time. Please help me to ID this situation. I've been reading countless hours and do not know where to turn for help. Thank you in advance.

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