Sounds normal to me. The mature leaf starts to die off and when the plants decided its not salvagable it will divert nutrients through the dying leaf to the plantlets that form on the edge of the leaf. Is it the whole plant dying or just a leaf at a time? They are unsightly but if you leave it there you get more plants! If you don't want the new plantlets cut the entire leaf off as soon as it starts decaying and the plant can put those nutrients to new growth.