Gray tree frog identification

Hello,

I am wondering if the dark spots on the tail fin and musculature in gray tree frogs/Cope's gray tree frogs become more dominant in the later stages of the larval period. I am currently trying to identify tadpoles and am unsure if the tadpoles I am looking at are spring peepers or early-stage tree frogs. I am from Minnesota and do not know if finding spring peeper tadpoles is still possible in early July.

Thanks,
Jeana