If you are comparing grain in slides to grain in B&W film - yeh - they are grainy - all the silver grain gets bleached out in color. One way to tell if your film is underdeveloped is to look at the printing on the edges (roll film only) - if they are dark and crisp and your images are weak - you have an exposure problem. If the lettering is weak - you are underdeveloping (unless you are compensating for contrast - I rate most of my film slower and develop 1 stop less to keep my contrast correct for #2 paper in a condenser enlarger.)