This is how POS work. After a successful stake, the coins are split into two blocks.
(In BALLS coins are not split if coinage > 2 days: https://github.com/iGotSpots/BALLS/blob/0a2871ee77defdb19d318c828b743b3299ff76db/src/wallet.cpp#L1215)
Here you have an example of all blocks splitting: http://balls.blockexplorer.cc/address/SdgVFhwTYYzajAXbAUfkDSvcKNwW9RgCd3
And here http://balls.blockexplorer.cc/address/SNh8qLUtKWvyBf9y5ZjgHmg9STyuRbZKFs the first block is older than 2 days and does not split.