Tomato leaves just drying up

I've looked into a few things this might be, but curious as to what others' thoughts may be. Not seeing any webbing or any yellow spots or yellowing leaves. I did fertilize with granular 10-10-10 at the beginning of the season per the label instructions, but have been using all purpose liquid miracle grow, just to use it up because we have it, maybe once every two weeks and fish fertilizer once every two weeks. I haven't given the plants anything on the last month, though. The leaves just start turning brown and the stem stays supple but yellows and just falls off. It's also doing it pretty quickly on old growth. Nothing wrong with the fruit. Just the undercarriage. I have a micro that is nearly leafless. I thought maybe it was late blight, but wanted to get some other opinions. Any insight would be appreciated. I am not too anxious over it, as it is nearing the end of the season. It would just be good to know in case I encounter this again.