[BobandJack]

I have a few tomato plants that are growing away nicely but a few of the leaves are a bit manky, which I think may be magnesium deficiency so I'm assuming a bit of feed will sort that out . BUT I'm sure I read somewhere (possibly in Bob Flowerdew's book) that you shouldn't start feeding them till they've set fruit (which they haven't yet) so what to do?  Any suggestions?

[Ropster]

if they have a deficiency I would give them a feed , then wait untill fruit sets before feeding again

[peterjf]

feed them what they lack , get therm back on track then when ready , the tiny toms are showing , then feed proper ,

[Salmo]

I would give them a feed. The only reason for delaying feeding until the first fruits have set is that the plants will produce too much leaf.

[Kristen]

"I think may be magnesium deficiency so I'm assuming a bit of feed will sort that out"

If it is magnesium deficiency feeding with, say, a conventional Tomato fertilizer won't help.

Spraying with Epsom Salts twice, a fortnight apart, will fix the problem with seemingly miraculous speed

magnesium deficiency causes the edges of the leaves to go yellow, particularly the bottom leaves, and the veins to remain green.  It is noticeable in the early stages because the younger leaves loose their nice dark green colour, and you will start to see some lighter shades appear [which will eventually turn yellow].

More blotchy yellow patches may be virus instead.

[BobandJack]

I have fed them & they do look better but I also picked a few of the skanky leaves off & no more skanky ones have appeared.  I still have a lot of foliage & very few flowers & fruits though, probably not helped by my total misunderstanding of taking sideshoots off.  Several laterals (?) were taken off & several sideshoots left on in error  but hey it's all a learning curve right?  Next year will be different & if it comes to it at least I'll have loads of green stuff to go on the compost heap 

[Kristen]

probably not helped by my total misunderstanding of taking sideshoots off

This may help?

http://www.videojug.com/film/how-to-prune-tomatoes