I had problems with my zucchini's this year also. The plants never really got that big and in most years they are so large and full that I have to move leaves aside to see if there are zucchini's growing. and about 3/4 of my zucch's got what I think is blossom end rot - where they start out growing looking healthy but then the end of it turns yellow and ends up being mushy. I had quite a few leaves also that turned yellow so I just cut those off. I bought mine as starts this year and maybe they just weren't hardy starts, or maybe I didn't properly amend my soil with the right nutrients. not sure.