1. An image defect predictive diagnostic apparatus comprising: an acquisition unit that acquires first characteristic values and second characteristic values from an image forming apparatus that forms an image by using an electrophotographic process, the first characteristic values including at least one of (i) toner concentrations and (ii) developing potentials, the first characteristic values having an influence on developability, the second characteristic values being different from the first characteristic values; and a notification unit that predicts occurrence of a dot image which has no relationship with the image by using the first characteristic values and the second characteristic values which are acquired by the acquisition unit, and that makes notification.