There are subtle differences to the trained eye. For example, the dolphin on the right displays the distinctive "hump back" associated with the species while the one one on the left has a smoother rounder back seen in the Apaloides summersetus variant.
The dolphin our our right also features the uniform coloration expected, while the left dolphin has subtle variations on the ventral surface.
These kinds of discerning observations should not be attributed to stress, but to the keen powers of eyesight after age 50 :-(
also note that the dolphin on the right is utterly missing.
The dolphin on the right needs more cowbell.