Problems with elephant's foot
Elephant's foot can be caused by different causes.

Incorrect leveling or incorrect nozzle to bed distanceThis answer describes that it can be caused by a too low nozzle to bed distance.
Bed temperatureA too high bed temperature and weight of the print can cause bulging out of the bottom layers. This also frequently occurs as the result of an uncooled/too less cooled first layer.

Improved cooling, lowering bed temperature or adjusting nozzle to bed distance and proper leveling are the most obvious solutions to fight this problem. Other solution can be found in using chamfers on the bottom of the print (requires modifying the model) or printing on a raft, this latter solution does lead to losing the nice bottom layer finish.