Cut the fish filets into 2-inch square pieces or as close to it as you can get. Dip them, one at a time, in the ranch mixture, rolling to ensure it's covered evenly. Lift it, allowing excess to drip back into the bowl, then put into the panko crumb dish. Use your clean hand to toss some of the panko crumbs over the top of the fish piece, then flip to be sure all sides are covered in crumbs. Place it on the baking sheet. Repeat until all the pieces of fish have been coated. Lightly spritz the tops of the fish nuggets with non-stick cooking spray and put the pan into the oven. Bake for 15 minutes, or until the fish is firm to the touch and the bread crumbs are golden brown. Serve immediately with your choice of dipping sauces.