The things that help solidify the identify of female and immature hummingbirds are good pictures of the tail spread and/or clear pictures of the folded wings (preferably both). Vocalizations can be helpful too with certain species.
That being said, I think all of these are fine for Black-chinned Hummingbirds with the exception of #1, which feels like it's better left as selasphorus sp., with that long tail and significantly buffy flanks. It's likely a RUHU, but BTHUs are at this location and I'm not sure we could definitively rule it out based on the single photo provided. The tail spread photo (#4) is not a Rufous Hummingbird as the outer rectrices are much too wide and the base of the feather is not rufous. I think what you are seeing is the lighting of the photo and perhaps a reflection on the ventral view of the bird.