Hmm well they could in fact fade....Iv had people sit on some for two years before they faded but still leaving some black fin.
on the other hand true "high quality thai SRT" are already red/orange/peach color mostly faded out.
how much were these fish? and what size tank are they in,and they look like they have the red gene in them...the gill area is usually the 1st to get the red color.
also feeding them the right food is a biggie. I of course use a good high quality pellet for the red color (Hikari,spectrum,etc)and Blood worms and krill I also feed them my vejas veggie pellets now and then, along with different live food (not fish! mealworms, crickets,flys) Never wild the LFS sells them so I dont worry about pesticides