Left For Vacation and....

well i left for vacation for 4 days and i came back to a cloudy tank ive already done a 10 gallon water change and its still cloudy this morning any ideas? the coral still seem happy as well as the fish the only thing i noticed was the cloudiness and my brittle starfish 3 of its arms seem really short while i was gone my brother was to watch the tank and he said he didnt do anything but feed and turn the lights on the tank is a 40 gallon breeder