Strange edges on chocolate chip cookies

[Birdie814]

I found this chocolate chip cookie recipe that I liked and made it once and it was great. But every time I have made it since, the edges are a little dark and they split with little "v" shapes. The only thing I changed is I started using dark brown sugar instead of light brown sugar. I bought a oven thermometer and make sure the temperature is right... Does anyone know how I can stop getting split edges?

 

[retired baker]

You changed the recipe.

 

[Birdie814]

I’ll try returning to the original recipe. I changed it to dark brown sugar because I like my chocolate chip cookies to be a little darker and not so pale, but I’ll see if that corrects it.