[Aldebaran1981]

Hello Everybody,


I am new here and tried to find the answer to this question but don't seem to. I couldn't identify this illness/disease/irregularity on other gardening websites, either.

I have grown tomato plants from seeds, bought them in a shop (I mean they are not from an unindentified source). They germinated well, they were growing nicely, and when they were about 30 cm (12") tall, the best and healthiest looking plant started developing small, dry greyish-brown spots on the leaves which then grew to patches and eventually the whole leaf would then dry and die. It began with the bottom leaves and if I pinched part of the leaf or a whole affected leaf, new spots would come on the other leaves. This plant was kept separately due to space problems but the conditions were the same for all of them, later I transferred this one to the garden where the problem got much worse, now the plant is barely alive but the top leaves still seem to be OK (no spots). However, weeks later the rest of the plants (which are still in pots) started having the same problem.

I have really no idea what is this and I would be very grateful if someone could help. I have some experience with gardening but not too much and I'm very happy to receive advice. Thank you.

[Stree]

Not sure myself, could it be leaf miner?
This might not be the answer but it will bump your post so someone more knowledgeable is likely to see it.

[Aldebaran1981]

thank you! I think it's not a problem caused by an insect or worm, they were kept indoors when the problem started and I couldn't see any insect on them when I closely examined them.

[Aunt Sally]

Looks like tomato leaf mould, cold damage, and sun scald to me.

When in the greenhouse they needed more ventilation to drop the humidity, especially overnight. 

I think now they are planted out (were they hardened off well?) they have been too cold at night, this has given them the purpely tinge.  The brown patches can be caused by too much sun on damp leaves.