Photon overcompressed an image

I’m using Photon. I published a post containing a photo just now and noticed that the published photo hosted on Photon had the telltale blocky look indicating a high JPEG compression level. When I turned off Photon, the image quality improved.

This particular photo had a large expanse of off-white wall, which often makes compression artifacts more noticeable.

Is there a way to disable Photon on a specific images in situations like these?