could be alot of things. can you post a picture so we dont have to guess?

Photos

Here is a link that might be useful: photobucket

no images at link

Trying again

Here is a link that might be useful:

are they in ground or containers? but looks like you have a nutrient problem. its hard to tell with that picture. it looks close to a magnesium problem. what kinda fertilize are you using?

The interaction between nutrient mobility in the plant, and plant growth rate can be a major factor influencing the type and location of deficiency symptoms that develop. For very mobile nutrients such as nitrogen and potassium, deficiency symptoms develop predominantly in the older and mature leaves. This is a result of these nutrients being preferentially mobilized during times of nutrient stress from the older leaves to the newer leaves near the growing regions of the plant. Additionally, mobile nutrients newly acquired by the roots are also preferentially translocated to new leaves and the growing regions. Thus old and mature leaves are depleted of mobile nutrients during times of stress while the new leaves are maintained at a more favorable nutrient status.

The typical localization of deficiency symptoms of very weakly mobile nutrients such as calcium, boron, and iron is the opposite to that of the mobile nutrients; these deficiency symptoms are first displayed in the growing regions and new leaves while the old leaves remain in a favorable nutrient status. (This assumes that these plants started with sufficient nutrient, but ran out of nutrient as they developed). In plants growing very slowly for reasons other than nutrition (such as low light) a normally limiting supply of a nutrient could, under these conditions, be sufficient for the plant to slowly develop, maybe even without symptoms. This type of development is likely to occur in the case of weakly mobile nutrients because excess nutrients in the older leaves will eventually be mobilized to supply newly developing tissues. In contrast, a plant with a similar supply that is growing rapidly will develop severe deficiencies in the actively growing tissue such as leaf edges and the growing region of the plant. A classic example of this is calcium deficiency in vegetables such as lettuce where symptoms develop on the leaf margins (tip burn) and the growing region near the meristems. The maximal growth rate of lettuce is often limited by the internal translocation rate of calcium to the growing tissue rather than from a limited nutrient supply in the soil.

When moderately mobile nutrients such as sulfur and magnesium are the limiting nutrients of the system, deficiency symptoms are normally seen over the entire plant. However the growth rate and rate of nutrient availability can make a considerable difference on the locations at which the symptoms develop. If the nutrient supply is marginal compared to the growth rate, symptoms will appear on the older tissue, but if the nutrient supply is very low compared to the growth rate, or the nutrient is totally depleted, the younger tissue will become deficient first.

It looks like a magnesium deficiency from the picture but it is blurry so hard to say.

Growing them in containers.
Using Miricle Grow and fish emulsion as fert.
Have noticed some of the small weeds in the containers have the same symptoms, yellow leaf edges with the veins still green.

Thanks for help.

"Have noticed some of the small weeds in the containers have the same symptoms, yellow leaf edges with the veins still green."

That is called chlorosis. It is due to a mineral deficiency. The mineral deficiency can be due to not enough minerals in the soil or due to the soil having a pH that is preventing the plant from absorbing the minerals or due to too little/too much water preventing the plants from absorbing the minerals or compacted soil/poor drainage harming the roots and preventing the plant from absorbing the minerals it needs.

What soil/potting mix did you use? How much are you watering? If the tomatoes don't have blossom end rot, it is probably not a problem with too little water. Do you know the pH of your mix?

I think a virus can cause chlorosis in tomatoes, too, but if the weeds are affected, I don't think that is the cause.

My tomato plant lost it's foliage so I cut it and now it's just a stem. Is it possible that it might get new leaves and stay alive or it's going to die?

ketaki, that would depend on why it lost its foliage. If the root system is healthy and certain diseases weren't responsible for the loss of foliage, you might well get new stems and leaves. Tomatoes have an incredible will to survive, and can send out new shoots (and roots) from anywhere!

But this is the end of August. Unless you live in a very warm climate, there's not enough time left to grow new stems, leaves, and blossoms, and then wait a month or two for fruit to ripen.

They are in different mixes.

I fertilized today with magnesium.

Will see what happens.

Might cut them back and let them regrow - I'm in zone 9 so they have time.

Thanks all.

ketaki, I should also have added that some tomatoes are determinates, which mean that they naturally only grow to a certain point, after which they don't put out new growth. And then they die. [Indeterminates, on the other hand, keep growing until frost kills them.]

Do you know the name of the variety you grew?