If your hens were all (or almost all) laying and then stopped, there is a reason why. While bantams are known for broodiness (I personally always have one or two brooding at a time, ALL the time!), I think you would notice if they were all wanting to sit on the nest and acting crazy if you went near them! When my bantams are not brooding, they lay everyday.
I would want to know what happened to the one egg that was missing. If it's not a chicken eating the eggs, then it has to be a predator of some sort. If that is the case then they may not be laying due to the stress of whatever it is getting into the nesting boxes. Is there some way you could spy on them at night?
Cathryn