The two on the left are (I think) 心佛 which literally means "heart of buddha". There could be several ways to read this, but probably "Shinbutsu". Usually the stamps are the name or "art name" of the artist. This one, however, might indicate something else. I would guess the subject of the painting is some kind of religious (buddhist) theme.
Bottom right is 大空堂 (Daikūdō), which is probably the artist's "art name".
The other one is the head of buddha (or maybe the head of a bodhisattva).