Bridesmaids chose a dress with too much cleavage

Hi Brides! I have 2 Maid of Honors instead of bridesmaids (I just refer to them as bridesmaids for better understanding) that are my childhood best friends. I didn’t want to be too strict on what they wore so all I decided on was the color and that the dress was floor length, but I left the style up to them. I asked recently if they had any idea what they were leaning towards and was surprised to learn they decided on the same dress (they used Azazie) and had already ordered. When I saw the picture, it’s bareback with a deep plunge….more revealing than tasteful. I didn’t initially say anything because I would like to wait to see them in the dresses in person, and I was kinda shocked to find they ordered already without running it by me first? I guess I didn’t give any further instruction, but I also didn’t think they’d choose something so revealing. How should I approach this? Thanks brides!