Wouldn't there be some higher-altitude waters in Burma that would normally display lower temperatures? Are these fish perhaps found in cooler mountain streams? I'm not saying that they are, I have no idea, but there are many fish species that inhabit cooler waters than others at the same latitudes simply by living further up the mountain slopes.They come from Burma. They come from much warmer waters than that.
The members posting above have kept them successfully at cooler temperature. That is not 'The natural water temperature range that these fish are found'.
Looking at those lovely fish in the original post, I'd be hard-pressed to say that they are anything other than perfectly healthy, rather than temperature-stressed.