Rabbits have started kicking out their bedding

Question
Our two 6 months old mini lops have started kicking their wood shaving bedding out of their hutch and into the main run.  The hutch is outside in the garden.

Everything was fine for the first few months, with the hay neatly in a rack on the inside wall of the hutch and the wood shavings on the floor of the hutch. Now, they mix everything together and as soon as they have a chance, they shove and kick the stuff into the run, which leaves their main toilet area and night-time rest area completely bare and free of any hay/wood shavings. The run itself is grass, so they're in effect covering up this feeding area.

What's happening and why this sudden change of behaviour? As far as I can see, we haven't made any changes which could have triggered this.

Answer
Are they digging or trying to make a nest?  A number of rabbits dig, and will dig their litterbox or anything else they can find that will move.  

Can you fix it so that they can't dig the bedding out?  Maybe put plexiglass or something around that area so the bedding just stays in the hutch?

If they are nesting, then that behavior won't go away unless they are spayed.

Kim