Did you overcook them and dry them out?
I've made them a couple of times over the years and have never had them turn out like that.
Baked goods can be VERY sensitive to overcooking. Even if it doesn't look as if something is overcooked, the internal temperature can flash over to more than 212 deg. F, and that's the temperature at which all of the moisture in the baked good waves bye bye with a middle finger.