I found my platy fish dead this morning?

they probably don't have enough space i have a 10 gallon (39.9 litre) and the maximum i had was only 5 platies they probably got stressed out or they either got a disease. it is best if u keep say 6-10 platies in a 20 gallon aquarium.it is also natural to have a fish dead on the bottom then on the top.(for example my 6 year old goldfish was dead upside down,RIP:( ur temperature is fine but i would be just worried about the tank size.)but ur fish might have died in starvetion. and do u keep the fish with any other fish?