It's just what cichlids do, It's as natural as a dog wagging it's tail. Looks like yours have paired up, and are getting ready to breed. When breeding, they often dig out a "nest" like they would in the wild.
They dig when happy and content. Worry when they stop digging lol. Yours look happy content and stress free. You will soon have more jags than you can cope with.
Looks a lot like nest building you have there. As mentioned it's something many cichlids do, often in preparing to spawn or creating a nest or bower to attract a mate.