it is very possable temp , but i do know many people inc myself that have had sucsess in keeping auranti in full tropical all there lives , obviously sub-tropical temps should be aimed for , loosing within a couple of months would suggest not temp , as they experiance lower end tropical temps for nearly half of the year. so a couple of months is nothing to them. unless your temp is at the very top end of tropical temps.
what is your tank actually reading ?
i know several people who have raised auranti with no problem at tropical , the only real drawbacks are the fact that the colours are not as strong , they become less active the higher the temp , and they will def. not breed as they need a trigger point at around 20deg.
there is such a thing as auranti deseise. which is a very nasty bacterial infection that eats away at the fishes skin , it is very hard to treat and you only stand around 10% of saving the fish. this diseise can happen at any temp , i have had it at sub-tropical and suffered heavy losses. no one seems to know why or how they get it. it may well be something that is allready carried by the fish from the wild. i had my losses within 2-3 months of buying them. the ones i have now i have had around 6 months and they are doing great and pairing up well ,
i would suggest you maybe try and locate them from an alternitive shop
cheers col
another option is to run with chiller ... i think best is to stick with the tropical types ... 