Heh. I'm assuming you want C&C, but you're doing way better than I'd do if I tried. So take it for what you paid for it.
Amber #1 - Need more fill lighting. Arm (elbow) angle looks awkward, that hand should probably be pointed out instead of in. Nit - car doesn't look bad enough.
Amber #2 - Interesting pose - not sure if good or bad. Fill is much better. Not sure if I'd like it better with more of the jeep or not.
Natalie #3 - I like. Maybe a little more fill on the face, or you could be emphasizing the heat and like the contrast.
Natalie #4 - I like. Nit: her top is pretty wrinkled. There are some that would say the hands prevent you from seeing her tush. OTOH, that position emphasizes other attributes. Not sure how best to resolve or even if you want to.
Overall nit: it's hot & sunny, likely affecting makeup. But you knew that, duh.
Suggestion: a fan could liven the hair. Tough on location like that, I know.