This is the LL forum - but similar diet, so I'll answer anyway. Sometimes you will get loose stools because of the sweeteners, or because your body is learning to adapt to the new feeding regime - particularly the sudden influx of lovely nutrients!! Usually your body will adjust in a few days time.
Hope this eases soon, I didnt have any side effects like this, but as Deb says your body is adjusting to a different intake of nutrients and being liquid.
Seriously, I would not worry about it....different nutrients, different vitamins....mention it to your pharmacy if you are worried bbut I wouldn't be too concernd.
Yes - I had green ones near the beginning on LL! You're chucking out all sorts of crap so expect every sort of poo under the sun except for very big ones!