[Lardman]

Some please tell me this is just plant stress from the odd weather recently. 13/15 tomatoes are beginning to look like this. Im also seeing a lot of leaf curl and brittle leaves 

[Lardman]

Leaf curl. 

I've cut most of them of this afternoon without think to take a picture but this gives an idea.

[Sparkyrog]

I thought that was heat related but I may be wrong 

[mumofstig]

If it's only on lower leaves, I'd not be worried about it 

[Headgardener22]

My understanding is that Leaf Curl is usually heat related, caused by the night/day temperature variation. Our polytunnel has been hot in the day and cold at night so I expect some problems.

The other alternative is Aphids. But they usually make the leaves curl down rather than up.

So long as its not the new growth, they should be OK.

[Lardman]

If it's only on lower leaves, I'd not be worried about it 

Above the second truss on some plants.

The aphids seem to be heading for the pepper / basil this year. There are lots in the GH but I've not seen any on the tomato plants. To GH seems fine (only 3 toms in there) but the outdoor have the same on the lower leaves. 

I do hope I haven't brought in something nasty with those crimson crush plants....

[New shoot]

I do hope I haven't brought in something nasty with those crimson crush plants....

I don't think you have.  It looks weather related to me - the variation of temperature as already said and just the stress of the yo-yo weather alternating between cold, breezy days and hot ones.

Tomato plants can look really tatty and still produce a good crop.  Keep feeding them and they will grow though it 

[mumofstig]

Google magnesium deficiency on toms - could be that.

RHS advice here
https://www.rhs.org.uk/advice/profile?PID=456

[Goosegirl]

Having seen this topic on here before and Giggled it as well, I'm as sure as I can be that it is due to the wide variation between day and night temps in the greenhouse. Mine are just starting to go like that and have always done the same.

[mumofstig]

Curly leaves caused by temperature variation have always shown on the top leaves of mine - not seen it before on lower leaves.
There's always a first time though 

[Snoop]

I've got a few that have gone like that too. But other than these and some of the very bottom leaves that are yellowing, the rest of the plants look very healthy. I've decided not to worry about it.

[Dave NE]

I have one like that out of 20 and it is much smaller then the rest, I call it the runt of the litter but I have been worried about it, any leaves I take off are straight into the bin and I wash my hands, Dave

[Headgardener22]

If you've got yellowing lower leaves, it could be Magnesium deficiency. If the plant is short of magnesium, it takes magnesium from the lower leaves to use higher up the plant (so the lower leaves go yellow). Magnesium deficiency can be caused by over fertilising the plants. Potassium gets taken up in preference to Magnesium so you might need to increase the magnesium feed with epsom salts either watered in or misted onto the leaves.

[Salmo]

I am sure you are spot on HeadG.

Give them some Epson salts as foliar feed. It will not cure the affected leaves but it should stop the other leaves being affected.

[mumofstig]

I'm glad you both agree that it could be magnesium deficiency 

Google magnesium deficiency on toms - could be that.

RHS advice here
https://www.rhs.org.uk/advice/profile?PID=456