Complete change? Both "Space Seed" and TWoK featured an all-Aryan collection of goons. Supposedly, there were non-Aryans in "Space Seed" somewhere off camera, as Scotty claims Khan's team was of mixed race and we get the impression Khan woke up even those among his seventy-something followers who weren't of pure blood... But the same could apply to TWoK.
They also all turned blond. And were somehow all younger. Although admittedly we didn't see all 72 in "Space Seed"
Why should we think Khan would have chest hair? For all we know, he was unable to grow a beard, too... "Shaving" doesn't really fit, as we'd see stubble after nearly three centuries of sleep.
Marla of course wouldn't know if Khan had some hair growth defect or was perhaps engineered to be a dolphin. Her line about him being "probably a Sikh" is completely flawed.