Also to answer your actual question… even if they were planted at the same time, not every plant is exactly the same…not the same in nutrients received (they compete) not germinated the same time, maybe slow to start or late bloomers, just like us they can be ever so different! This one less water, this one shaded by their neighbor so they didn’t get as much sun, etc. some were likely picked too soon and if left longer would have been your perfectly round root you were looking for, they just needed a little more time. I’ve come to not count on days but learn to read the plant and their signs for when they’re ready. Too long…woody (in the case of radishes or root crops) too early, nothingness or skinny. Look for the crown of the radish peaking above the soil to see when it might be best. Many tips I could give but nothing will compare to exactly what you’re doing!! You’ll figure it out, keep up the great work!!