I've been lucky enough not to experience this, although i've heard quite a few people do go through a spotty stage. I think it's really just your body's way of detoxing and in no time you'll be back to lovely glowing skin.
Yeah, I woke up this morning to an emerging spot on my chin!
It's usually only temporary while your body 'purges' and a lot of people find that, because of the volume of water they're getting and having all the right nutrients, their skin is actually much better than 'normal'.
(of course it could also be that some of us end up spending a ridiculous amount on beauty products in place of food treats)