No, it's not. I dont think your clones are flowering, clones usually come from a mature plant, a mature plant puts out preflowers. after rooting and vegging for a bit your cuttings are now plants and since they are already mature they've started putting out preflowers. The first day of flowering depends, if your plant is mature when put into flower you can pretty much start your count the first day of 12/12 since the plant is ready and the flowering hormone will start the process as soon as its level of flowering hormone reaches the threshhold needed to do so day 1, you might not see it right away, but its happening. If your plant is not mature before flipping you count from when they first start putting out pistils or balls since they will still need to finish maturing and then they start the flowering process.