Subtracting each row from the one before it in MySQL

diff.sql

SELECT
	b.ts,
	b.ost_name,
	b.bytes_written - a.bytes_written,
	b.bytes_read - a.bytes_read
FROM
	(
		SELECT
			OST_DATA.TS_ID AS tsid,
			TIMESTAMP_INFO.`TIMESTAMP` AS ts,
			OST_INFO.OST_NAME AS ost_name,
			OST_DATA.WRITE_BYTES AS bytes_written,
			OST_DATA.READ_BYTES AS bytes_read
		FROM
			OST_DATA
		INNER JOIN TIMESTAMP_INFO ON OST_DATA.TS_ID = TIMESTAMP_INFO.TS_ID
		INNER JOIN OST_INFO ON OST_DATA.OST_ID = OST_INFO.OST_ID
		WHERE
			TIMESTAMP_INFO.`TIMESTAMP` >= '2016-06-04 00:00:00'
		AND TIMESTAMP_INFO.`TIMESTAMP` < '2016-06-04 00:00:15'
		AND OST_INFO.OST_NAME = "snx11025-OST005c"
	) AS a
INNER JOIN (
	SELECT
		OST_DATA.TS_ID AS tsid,
		TIMESTAMP_INFO.`TIMESTAMP` AS ts,
		OST_INFO.OST_NAME AS ost_name,
		OST_DATA.WRITE_BYTES AS bytes_written,
		OST_DATA.READ_BYTES AS bytes_read
	FROM
		OST_DATA
	INNER JOIN TIMESTAMP_INFO ON OST_DATA.TS_ID = TIMESTAMP_INFO.TS_ID
	INNER JOIN OST_INFO ON OST_DATA.OST_ID = OST_INFO.OST_ID
	WHERE
		TIMESTAMP_INFO.`TIMESTAMP` >= '2016-06-04 00:00:00'
	AND TIMESTAMP_INFO.`TIMESTAMP` < '2016-06-04 00:00:15'
	AND OST_INFO.OST_NAME = "snx11025-OST005c"
) AS b ON b.tsid = a.tsid + 1;