Also, when you get creatures in so big area (28 x 23 SQM), you should use getSpectators to save CPU, it will iterate over tiles in C++:
OTX2: getSpectators(centerPos, rangex, rangey[, multifloor = false])
TFS 0.4: getSpectators(centerPos, rangex, rangey, multifloor, <optional> onlyPlayers)
TFS...