Are all plants grown in buckets? What are you using for soil? And can you be more specific as to what you mean by, "when I go to pick them the next day they're already bad". Any pix of the bad ones?

Also, there is a Tomato Pest & Disease Forum. It is more active than this one.

tj

Do you have drainage holes in the buckets? Why it is almost no soil in them?

Almost looks like bottomless buckets?

tj

Your pepper leaves are puckered? I would check the backside of the leaves first for sucking insects (aphids, plant bug, leaf hopper).

The tomatoes seem to be damaged more on the bottom of the plant than the tops. Judging from the photos and the area you are in I would guess you are hit with early blight. I am in Wisconsin too and early blight and septoria leaf spot are bad some years on tomatoes.

It may be from the walnuts but doubtful. Tomatoes will not grow well by black walnuts. They will develop hollow stems that break easily. I have first hand experience with this.

Normally if the walnut tree is too far away or too small you will be ok. As the tree gets bigger and the roots get into the garden area you may have a problem. Walnut roots will have juglone that is toxic to many plants. Move the garden father away from the walnut or cut down the walnut when this happens. The juglone levels will subside with time. However I do not think your problems are from the walnut trees at this time.

To prevent comon tomato diseases, always limb up the lower branches to about 18"-24".

This helps as often on septoria asthe spores splash up from the ground. Yo also get better airflow under the tomato as wet, damp leaves will be more prone to tomato foliar diseases. Others use a mulch under the tomatoes be it plastic or organic.

Finally if necessary, a preventative spray with a fungicide containing the active ingredient

"chlorothalonil" will prevent most tomato fungal diseases. One common brand is "Fungon-il" that is an Ortho product. Many home growers in the US have to spray with a preventative fungicide or they will be wiped out by early blight.

Thankfully I grow an old heirloom variety and so far have had no blight issues despite my neighbor who grows tomatoes not far from my garden. His tomatoes get wiped out every year by early September due to early blight and septoria leaf spot. i never spray my tomatoes and hope my luck continues.

Also, be careful about any mulch derived from tree material. If there is any walnut wood in the mulch, it can damage tomato and related plants. Walnuts produce an enzyme that prevents the germination of woody plants. It is so effective that it will prevent its own walnuts from germinating. It is a strategy that prevents competition from other trees by not allowing those to grow within the drip line of the tree. Usually, new walnut sprouts were 'planted' by squirrels who buried the nut a distance from the parent tree.

Walnut trees too far away for roots to harm tomato and pepper plants; Maybe and maybe not. Are the walnuts to the west of the garden? The prevailing wind in Madison in the fall is westely. Perhaps your garden is peppered with walnut leaves. Another common practice that I did in the past and I suspect that others might do the same, and that is to put yard rakings on the garden in the fall. If you do that, omit the walnut leaves and twigs.