[AlistairMcLennan]

I fed my tomatoes some tomato food the other day, now the leaves appear to be developing brown marks.

Picture attached for some advice.

Thanks

[Kleftiwallah]

Looks like a touch of blight,    I should remove and burn them A.S.A.P.   
Cheers,   Tony.

[Scullion]

I have something similar with my tomato plants...



Two of the small leaves at the bottom have gone yellow. Another one has gone dark green and withered up like it's going to fall off, but suppose that could be down to careless damage caused.
As you can see the rest of the plant upward appears to be fine. It is watered regularly and grown indoors!? However, no feeder has been used yet as too early!?

[sunshineband]

These are just lower leaves dying off. I shouldn't worry too much.

Start feeding when there are tiny tomatoes in the first truss 

[mumofstig]

There has been no recorded blight yet this year, and it is even less likely if the toms are in a greenhouse.................don't panic yet   wait for other opinions.

Scullion yours could be a touch of botrytis, remove the leaves and make sure there is enough ventilation in the greenhouse.

Or as Sunny says ..just old age  

This site http://aggie-horticulture.tamu.edu/archives/parsons/vegetables/TOMATO.html
says

What could cause the leaves of my tomatoes to turn brown along the edges?
A. Leaf-burn or scorch generally indicates root injury, quite often caused by heavy amounts of fertilizer applied too near the roots. This injury often results in browning and die back of the ends and margins of the leaves. Other possible causes are root injury caused by nematodes, insects or physical injury by cultivation. Also overwatering or underwatering

[Scullion]

Thanks guys.

Cheers mumofstig, found that Qs and As quite helpful.

[AlistairMcLennan]

Thanks for all the replies.

The plants are starting to produce fruit so I will just need to wait and see how it goes.

Do I need to cut off the dying leaves or just leave them?

AL

[mumofstig]

Might as well cut them off as they are not green they are not making food for the plant