Homemade cookies...good at first then not so good later? What's the best way to store cookies?

When my white chips cranberry walnut oatmeal cookies come out of the oven (made from scratch), they are amazing. They taste crunchy toward the edges and soft in the middle. Then the next day they taste...kind of like scones. The texture is not right; they are too chewy and not soft enough...and they have lost their crunch. I've made them twice and the first time I stored them was in a tupperware container, and the second time in a plastic bag. Both times the cookies lose their great texture. I do cool the cookies on a cooling rack so I don't understand what's going wrong with storing the cookies. What is the best way to store cookies to maintain crispiness/softness?