Are my tomatoes sick?

[colliebird]

I bought a greenhouse during winter and am using it for the first time.
I'm growing tomatoes in containers, and did it with great success last year in a couple of green plastic "greenhouses" then put the plants outside once the risk of frost had passed.
My tomatoes in their containers are coming up fine in the greenhouse except a noticed about a week ago, one of the plants, which are now about 10-11 inches high, that the tips of the leaves are patched with white, which I thought might have been due to me having splashed the leaves when watering. Now the plant next to it has started with the same patches.
All the tomato plants this morning have little drops of water on the tips of their leaves!!!! It rained heavily here last night, but the tomatoes are in the greenhouse!!!!
Anyone seen anything like this before and what is it and what can I do?
I've taken an example leaf to the local garden centre, but they don't know and are pretty useless when it comes to veg subjects cos they specialise in flowers and decorative plants.
HELP


Valerie

[Flummery]

It's condensation. Not much you can do except leave the lights open a bit - which you don't want to do if there might be a frost. It won't seriously harm the plants. It's another reason I'm still bringing mine in at night!