There are several reasons that this could happen. One thing is that it might need a touch more flour. Baking can be tricky when it comes to measurements. If the recipes have weight with the ingredients and you have a scale, it is better to weigh. It is the best way to get the correct amount. Another reason is your oven may be running on the hotter side, which causes your cookies to be overbaked. I check on mine about a minute or two before the recommended time.