pH, maybe? Have you had it checked? What you describe sounds like an acidic soil problem I've seen, but it could be other things--which I'm sure you'll hear more about as this thread developed.

Well, I would check on soil quality/properties and soil chemistry first. Then, "review" to the best of your ability the rainfall history of the past season and your watering practices. If water was adequate, probably a soil chemistry/fertility issue, or could be improper soil aeration.

When plants fail the thrive, assuming they have adequate water and sun, it is almost always a problem with soil properties, chemistry and fertility. Do you have an excessively high pH or excessively high soil salinity -- you live in the West, where that can happen (although I think that's more of a problem in Nevada and Utah than in Colorado). What is the soil like -- loose and loamy, or dry sand, or hard, adobe-like clay? If it's not rich and loamy, you may need to add more organic matter, plus something to open it up like perlite if it's compacted clay.

Also, my personal opinion is that the 1-2-3 type fertilizer is so dilute that it's like not fertilizing at all. Did you have any other signs of nutritional deficiencies, like a purplish or yellowish tone to the leaves, or any irregular leaf coloration like dark veins and pale leaf tissue -- these can be signs of deficiencies, of which there are many, although the specifics vary from plant to plant and nutrient to nutrient.

It sounds like you want to be "organic," so I don't know what fertilizer options you have, but I would suggest that you probably need to fertilize more. I use a season-long timed release fertilizer like Bayer Advanced when first planting, and about 3 or 4 applications of a 20-10-20 all-purpose type throughout the season, depending on the crop. Since using the Bayer for the past few seasons, things just thrive for me -- for example, I picked over 40 bushels of tomatos this year, over 150 butternut and acorn squash, several bushels of sweet potatos, about 30 dozen ears of sweet corn, and so much zuchinni it got tiresome. I'm still picking escarole, lettuce, chard, and cabbage from under tarps. The Bayer is similar to Osmocote, but considerably less expensive.

Build your soil this fall and winter with lots of organic material--leaves, kitchen compost, manure, whatever you can get. Till it in in spring. It takes several years for an organic garden to recover from the use of chemical fertilizers and sprays. If you don't see lots of earthworms, your soil is not very healthy.

Also, most veggies need a minimum of 8 hours of sun. Save the shadier areas for lettuces and other greens that can get by on a little less.

Get a good book on organic gardening and don't give up.