It is hard to determine from just the perspective of pictures, but they do look a little bit like translational slumps.

Basically, there is a very weakly bonded layer somewhere in the slope. (It is the same process by which a snow mass fails in an avalanche.)

For soil masses, it can be worsened by freeze/thaw cycles.

Where will the water level be on the rip-rap in the first picture when your pond reaches full pool?

When the pond is full, the weight of the water will actually help push back against the soil that is trying to slump.

I would definitely keep an eye on it. You probably need to do some minor repairs before any heavy spring rains start. Those cracks will be erosion "magnets".

Hopefully, one of the dirt guys will drop in and give you some actual expert advice.