Tomato SOS

Please help!

Located: Mid South Island, New Zealand

Does anyone recognise what this could be? It looks like it has taken over one plant and is moving across to the others.

I have just been away for a few days and they didn't look this bad before I left!
It hasn't been too hot and it has rained but not 24/7.

I would like to try and save the ones that are fruiting if I can. They are the ones with little evidence.