Sometimes they shed fairly frequently, especially when they are young and growing.
In my case, I have a 4 year old adult that was clearly underfed (I'm being generous) before I got him, and has also made it through a bout with a respiratory infection. He is now in his third shed cycle since just before christmas. He's also gained 50 grams.
They'll also shed to replace damaged skin, but Zig Zag is probably just growing for you.