Squash problem

Hello my name is Doug and I live in central California. I've got an issue with my yellow crook neck summer squash.. The leaves come on beautiful and green but then turn yellow and the fruit is not doing well ether.. What's puzzling me really is they are planted in the same bed as my zucchini plants are and they are doing great.. Nice plants green and health and producing wonderful abundant fruit. Any suggestions to get them fixed up and going would be very much appreciated.