Well the tomatoes were all on staging next the cooled hotbed, and put on the hotbed in the evening, i filled the hotbed during the day.
I think it’s some kind of bacterial wilt – it can be brought on by high temps & humidity , also affects capsicums and aubergine! Apparently a big problem in Florida where humidity is always high,
So i introduced both a big dose of humidity and heat overnight and enter the bacterial wilt, waiting for its moment…
My chillis and aubergines, also on the hotbed overnight , are affected but luckily not too badly, but i may well lose some plants of those as well…
So I have moved my aubergines and chillis to the other tunnel, to isolate them from toms, which are still in the hotbed tunnel, but on staging.
I’ll take some more photos to show the symptoms of all the plants, doesn’t look promising, as once the bacteria takes hold it could just be a matter of time…. 
Yes a shame as they were all doing very well! And my first attempt at growing these plants from seed..
But it’s gardening and all failure is a lesson, and also a good time to practice the art of zen detachmenet 
But it’s hard as we gardeners do get attached to our plants…
I’ve pricked out some extra basil and i have 40 melons in modules, on the hotbed now, along with my curcubits, so all is not lost!