I have a very low tech planted 180g com tank. I've gone for the hardiest plants I can due to it being low tech. Amazon's are meant to be one of the hardiest and yet, as with yours, all mine developed the holes, and then discolouration, and then leaves rotting etc etc. You think they're going to die on you but just give them time to adjust. I just kept clipping the dying leaves off and in time new leaves will emerge and your plant will start to perk up.
Though in my experience, the plant won't develop the huge lush green leaves that you bought from the shop, they'll still be nice and green though a lot smaller. I just put this down to the fact that my set up is low tech and if I wanted huge lush green leaves on my amazons i'd have to upgrade from low tech.