Weird egg!!!

[paddyg84]

Got my first soft shelled egg yesterday. My 4 hens have been laying now for the last 4 weeks and every egg has been perfectly shelled. Even harder in my opinion that shop bought eggs. Thy also always lay in the nest box or occasionally on the floor near it. Yesterday on my return from work I found a burst soft shelled egg under the roost. The roost is just out from the wall and there is egg white down the wall. It's almost like she laid it while on the roost and fired it at the wall.
Any ideas as to an explanation as why I would randomly get an egg like this when all the others have been perfect and their diet hasn't changed?

 

[SarahInAlaska]

I had girls laying just fine and then BAM! 3 soft eggs in three days. Plenty of everything they need. I think they just have some weird ones every once in a while.