Well, I'm not an expert by any means (brand new to this). Anyway, I've been looking through the pictures on the problem solver thread belowto diagnose my own problems and yours looks more like early blight to me from the pics. It also looks like salt damage, or from the pics I've seen anyway.
http://aggie-horticulture.tamu.edu/tomatoproblemsolver/leaves/salt.html

Good luck and sorry you've got sick plants.

What's the soil situation like -- soil type, any amendments?

Have you fed them at all?

I'm thinking that's an odd pattern of yellowing you've got there... it almost never starts from the base of the leaf like that. Whitefly can cause some yellowing on older leaves and saps vigor, but you didn't mention how well the control is working.

If you haven't fed them, the first thing I'd try is a balanced fertilizer. That uniform yellow color isn't early blight (EB has dark spots); Verticillium tends to make the entire plant sag during the day as if it had gone dry, and can affect some branches more than others. I wouldn't rule out V. wilt yet, but try the fertilizer first, and check the levels of whitefly on the plants.

--Alison
who has had some of the same problems in the past, with weak soil... until the mites would come in and demolish the stunted little plants. Too much nitrogen is bad, but it is possible to have too little as well.

(by the way, that "salt damage" picture in the Problem Solver is a really poor one. It looks like every case of The Yellows from any cause, and it makes people invariably assume that if they have yellow lower leaves it's from salt. I really wish they'd take that picture out, since a hundred different things can cause a leaf to look exactly like that.)

--Alison
who thinks that the other pictures are fairly good...

i have some plants that look exactly the same!i thought maybe it was powdery mildew but im not sure.....?
i did give them plenty or miricale grow when they started.so i dint think its that.as for white fly im not sure but i dont think so....
let me know what you find out maternewb.

Thanks for all the help guys. I haven't fertilized for about 2 months or so, since fruit started setting. I will try today to add some fertilizer.

This is my first real season of gardening and I didn't necessary ammend my soil much. I have mostly clay soil, so I just put in some miracle grow mix and also some clay soil conditioner. Not much else.

I'll let you guys know how it turns out!

Early blight.

maternewb....was wondering how your problem turned out? My plants are looking just like yours and was hoping you were able to pull your plants through and pass along info. Hope you see this soon, cause my plants are on a fast downhill roll.
Peggy

I had a similar problem this year and though I can't tell you for sure that it's blight, mine responded well to copper fungicide sprayed into the surrounding soil; I sprayed somewhat on ther leaves as well but most of what had turned yellow was unsave-able, but I got tons of perfectly healthy new growth after spraying.

I went into my greenhouse this morning to find my tomatoes had developed purple blodges on their leaves and look like they are wilting. I have a cucumber in there to that has yellow bottom leaves turning brown but the new leaves come through green, the friut has started to look like they are rotting (its all female veriety) I have aubergines peppers and chillies in there to. The aubergines look like they have a very fine condensation on the leaves. I dont know whats happened to my greenhouse overnight.
Please can anyone help, I can only hope someone can give me some positive hope but Im not sure you can.