Looks to me like they are lacking magnesium but I'm no expert.

Scientific Name
Alternaria solani

Identification

Circular to angular spots with dark, concentric rings (target spots) develop on the older foliage
Severe infections spread to younger leaves
Lesions become quite large and are often associated with considerable leaf yellowing
Fruit infections are not common, but may appear as a blackened area at the stem-end
Often Confused With
Bacterial Canker (Early blight may cause browning of leaf edges, similar in appearance, but a lighter brown than bacterial canker symptoms.)
Septoria Leaf Spot (Early blight lesions grow much larger than Septoria lesions.)

Period of Activity
Early blight overwinters in infected crop residue. Spores are present throughout the growing season and may be carried long distances in the wind. Temperatures of 17- 24�C (63- 75�F) and extended leaf wetness favour early blight development.

Scouting Notes
Early blight lesions can be distinguished from other lesions on the foliage by the presence of concentric rings.

Thresholds
Where available use the TOMcast program. If this is unavailable, begin a preventative spray program when the first fruits are about walnut size. Repeat sprays as necessary. Repeat at 5- 7 day intervals during continuous moist weather. Extend the schedule to 12- 14 days in warm, dry weather if diseases are under control. Applications should continue until close to harvest.

Advanced
Scientific Name
Alternaria solani

Identification
The first signs of disease often appear deep in the canopy where the leaves stay wet. Lesions first appear on leaves as dark brown to black spots, 8- 13 mm (5/16- 1/2 in.) in size, on older foliage, but can grow much larger. Spots are circular to angular with dark concentric rings (target spot). The tissue surrounding the spot may be yellow. Lesions become quite large and are often associated with considerable leaf yellowing.

If the disease is severe, lesions also appear on younger leaves. As lesions enlarge, their shape may become irregular. They are often bordered by leaf veins.

Early blight may cause browning of leaf edges. Lesions may coalesce to form large dead areas on the leaf. Lesions may also appear on stems and blossoms (a cause of blossom drop).

Fruit infection is uncommon, showing up as a blackened area, similar in appearance to blossom-end rot, but at the stem end of the fruit. Fruit symptoms are most common late in the season, especially when extended wet periods occur at harvest.

Often Confused With
Bacterial Canker (Early blight may cause browning of leaf edges, similar in appearance, but a lighter brown than bacterial canker symptoms.)
Septoria Leaf Spot (Early blight lesions grow much larger than Septoria lesions.)

Biology
The fungus that causes early blight survive on decayed plant material in soil and can be seed borne. It is spread by wind.

Period of Activity
Early blight overwinters in infected crop residue. Spores are present throughout the growing season and may be carried long distances in the wind. Temperatures of 17- 24�C (63- 75�F) and extended leaf wetness favour early blight development. Unless the fungus is present on transplants, lesions generally don�t show up until flowering.

Scouting Notes
Early blight lesions can be distinguished from other lesions on the foliage by the presence of concentric rings.

Thresholds
Where available use the TOMcast program. If this is unavailable, begin a preventative spray program when the first fruits are about walnut size. Repeat sprays as necessary. Repeat at 5- 7 day intervals during continuous moist weather. Extend the schedule to 12- 14 days in warm, dry weather if diseases are under control. Application should continue until close to harvest.

Management Notes

Reduce early blight inoculum by following a 3 to 4 year crop rotation.
Ensure transplants are healthy and free of disease.
Cultivars vary in tolerance to early blight.
Overhead irrigation can promote foliar fungal disease due to longer periods of leaf wetness.

So this is definitely early blight Terrybull?

nycgarden it would be great if you could let me know how those leaves progress.. I'm interested in knowing what happens if you don't snip those off

not definite but i was showing what to look for and the defimition of earley blight.

earley blight lesions can be distinguished from other lesions on the foliage by the presence of concentric rings.

heres what it looks like.
{{gwi:41788}}

Strip off infected leaves,put in garbage bags ,dispose of.
You may still get some toms.
When done growing dispose of all planting mix .also mulch if used.
Dilute 1 part Bleach with 10 parts water ,clean your containers ,tools, wooden stakes,etc.
They say it overwinters in soil and plant debris.
I had this last year and because I didnt clean my containers last year I have it again.
So you can learn from my mistakes.

Hi,
Thanks for the replies. It may be early blight. A friend who grew some transplants for me has a really bad case of EB on her toms. The only reason I have some doubts is that I don't really see rings on the leaves. Also, it seems to be concentrated on the top of the plant. I would expect to see EB on all of the leaves, no?

What I hope is that my plants have gotten so big, in terms of the pots that they are in, that the roots of the new shoots at the top of the plant are getting suffocated.

I'll take a closer look today to see if I can see concentric circles and report back. Thanks for all of the advice. I will certainly be cleaning my pots and tools with the bleach solution just in case.

Hello fellow gardeners,
I took a closer look and didn't see concentric circles in the brown spots on the leaves, so I don't think it is early blight. I will be using the diluted bleach cleaning at the end of the season just to make sure though.

Thanks for your replies.

It doesn't look like early blight to me. Tomatoes are so susceptible to so many diseases that they'll break your heart. But, in most cases I've encountered the various fungal diseases start near the bottom, in older leaves. It looks more like a fertilizer issue to me. Given your regular feeding, I would be a little more worried about over fertilizing or imbalance than underfertilizing. I would take a wait and watch approach since you have good growth and production. Maybe slow down on the fertilizer and be careful not to over water in a peat based mix.

its not fertilizer, there would be whiteish brown edges not the blotches.
it is not over watering, they would be just yellow.

is it getiing worse or staying neutral?
if worse this would be my second thought.
{{gwi:41790}}

Yellow, uneven splotches on the leaves. Dead leaves that remain on the plant. Dead areas can be surrounded by a yellow circle.
No damage to stems evident.

Powdery Mildew, a fungus that infects weeds and crops in the solanaceous family.
Occurs late in the season.

Thanks Terrybull, Ohiofem, et al,
I don't think it's Powdery Mildew. I had that on my Zukes in the past and know what that looks like. The discoloration seems to be staying neutral for now. Interesting that it's only affecting the top leaves of the plant and not the older bottom leaves.

Any thoughts on the idea that it may be due to root bound plant that has outgrown its container?

I'll limit the fert. for now to see if that has any effect.

Thanks,