Help identifying a tomato problem.

peter.j.hughes · July 2021

Hi All, Can anybody identify this tomato problem? In the past I've grown tomatoes outside in growbags, but this year I'm using my shiny new polytunnel. It has no-dig beds with a good 4" layer of organic farmyard compost. All was going well, but in the last week or so several of them (about 5 out of 17) have been hit with this problem - see pics.

Image: https://us.v-cdn.net/6030279/uploads/editor/gx/ij5sx577khye.jpg

Image: https://us.v-cdn.net/6030279/uploads/editor/55/da6yeotdsagx.jpg

The lower leaves are broadly OK, if a little curled, but the new growth has suddenly died back, new leaves have yellowed and the top fruiting spurs have dropped all flowers. I initially suspected overwatering (dripline flow rate miscalculation!) or temperature fluctuations, but it's obviously more serious than that. Any ideas - early blight, wilt, herbicides .... etc.