I would say what you need to do is get a soil test for starters, and then compare the results to the requirements for the individual plants that you feel aren't performing to their optimum. From what I recall you can't get a soil test in California other than from a private lab or buying a soil test kit, perhaps Lyn or someone else from the state can advise on that.
Different plants can have different requirements as far as fertilizing, watering, pests and diseases are concerned, also pollination for those where the yield is a fruit. Any of those factors can influence optimum yield. Another factor is the number of plants needed for the expected yield and also the length of time needed from planting to harvest. For example, how many tomatoes did you need and how many plants did you have, and how long ago were they planted?. How long ago did you plant the cukes and what variety are they?
I have heard of "Amend" but am not familiar with it. I couldn't find what it consists of on Google because it is too common a keyword. What problem were you intending to correct with it? Did you add fresh coffee grounds to the soil or composted, and did you sow seedlings where you used it?
