Sudden collapse of container tomato
Two days after a good rain of one inch or more, and a day after I harvested my first perfect tomato from this Goosecreek tomato in a 25-gallon smart pot, it completely collapsed overnight. The other 11 pots growing eight different heirlooms in the same modified 5-1-1 potting mix (5 parts pine bark fines-1 part compost-1 part FloorDry diatomaceous earth) are doing great. Most, including this one, show some minor damage from septoria on the lower leaves, but they are mostly six feet tall or taller and have many green tomatoes. This one is actually much shorter than the others, but it also has more fruit on it.
The potting mix includes Dynamite all purpose CRF 15-5-9 and I have been using some Tomatotone and FoliagePro to feed every few weeks. I haven't seen much insect damage and have only treated for fungus a couple times with Serenade. I know some would recommend more aggressive treatment for disease, but in many years of growing tomatoes this way, I've never seen disease damage the fruits or stems enough to be a major problem. And I'm uncomfortable using anything stronger.
I watered the plant thoroughly after seeing the wilt, even though the mix was still damp a few inches below the surface and none of my other tomatoes needed watering. It perked up overnight, but collapsed again the next day and has continued to look worse each day. There are 16 fruits -- most larger than a tennis ball -- on the plant. The plant hasn't been exposed to herbicides. The weather has been just about perfect during the day with highs in the low 80s, although we did have overnight temperatures in the mid50s for several days in the week before this happened.
This happened once before many years ago to one of six tomatoe plants in containers, and I never was able to figure out the cause. In that case there were two plants in the pot. The first one wilted a week before the second one. After both were goners, I pulled them out and planted another tomato in the same pot. It did fine.
Any ideas what may be going on?