no they are not....why?
aquaman is from a race, that are almost identical to humans but becuase they live at the bottom of the ocean their bone and muscle tissue are fortifed against the extremely high pressures of the water, so the weakest atlantean is about 20 times stronger than a normal human, arthur himself might be a mutant tho, cuz he's a hybrid between normal man and atlantean princess. and he's about 20 times stronger than a normal atlantean, and hundreds of times stronger than a normal human
diana is made from clay, and animated by magic.
superman--no need to get into him
sups aint
wonderwomen aint
aquaman aint
so no they arent mutants the only one people might think is a mutant is aquaman but he is only a human atlantian hybred
calling aquaman a mutant would be as correct as calling Prince Adam(he-man) a mutant cause he is a human eternian hybred.
you should know prince adam is a hybred and his strength is higher then regular eterneians (thats without the Power of He-Man).