My eyes are slightly downturned - Am I a good candidate for a subtle Canthoplasty?

Each photograph is off in different ways. The best pictures are are done with the eyelid looking absolutely straight ahead. In each of these pictures you are looking slightly up, down, to the side. Bottom line, no you are not a candidate for a "subtle canthoplasty." Do you even know what that surgery does? Canthoplasty is being pushed as a cosmetic procedure. It is not a cosmetic procedure. If the surgeon gets this wrong (happens all the time) you will feel wrecked. I suspect that a detailed assessment will discover that you have mild pathology in the attachment of the levator aponeurosis that elevates the upper eyelid margin. You do demonstrate in this photograph that there is a compensatory left eyebrow elevation. So I do think something is going on here but no, you are not a candidate for a "subtle canthoplasty." Don't let yourself get harmed by well meaning surgeons who have not bothered to critically assessed what is going on here. Your eyes can be your best feature.

Your eyelids look completely normal. Make-up can give you the appearance you desire without surgery.
There is a surgery to raise the outside corner of your eye. But the risks of postoperative problems do no justify the surgery.