In reverse order, obviously Arnold, then Grimek. The first and second are tough. Someone else also guessed Howorth, but I’ve never seen a picture of him smiling so I can’t match it. Another guess is Larry Powers, so I have to research his pictures at the time. Haislop and Gironda are interesting choices, I have to check.
Third looks like Al Murray, National and Olympic coach in 50’s-60’s. I don’t know if he worked for Bob Hoffman.
First one I thought of Reg Park, because he was one of the few bodybuilders that smiled for the camera when lifting. Howland is possible, shape is right. Probably not Gironda cause he would never let anyone take a picture of him with abs looking like that.