Tomato Leaves

It could be the sun scorching the leaves through droplets of water. Cheers, Tony.

 

Looks a bit like insect damage to me, but not sure what.
If it gets no worse, I dont think I would be that bothered.
It could well sort itself out.

 

I'm with Pete on this. My guess is that it's red spider mite. If it is it will spread unless you get on top of it. You can slow it by keeping the plants moist by misting and raising humidity. Neem oil, if you are organic, will work to a certain extent and you can also introduce predators such as phytoseiulus.
The plants you moved outside will probably recover as rsm needs hot and dry conditions. But if it is rsm you'll find the remaining plants in the GH may well become infected.