I refilled the whirlpool and added Lotus Clean to the fresh water. The water turned a milky colour - why is that?
This is a normal reaction. As Lotus Clean starts to work, it encapsulates impurities in the water. This is what causes the discoloration. This is especially true of whirlpools that have been in operation for some time, because Lotus Clean dissolves biofilm which has formed in the tubing.
Please clean the filter the following day and increase the filter's running time. The cloudiness usually disappears within a day. In particularly severe cases, the water may remain cloudy for up to three days.