just a tip for the future, if you buy the fish and take them home in a bag, let the bag(still closed and with the fish in it) sit in the tank for 15-20 minutes and then transfer the fish without the water from the bag, this will let the guppies adjust to the temperature, another thing i do (i don;t know if it helps but i do it anyway) is put the fish in a bowl with 50% water from the bag and 50% water from my tank, i think this helps the fish adjust to the variouse ph and hardness
i hope this helps, and remember, fish deserve to be treated as well as us!