A couple of things here. As I suggested Friday, it could have fire blight. AS later stated, fire blight is systemic, therefore no amount of contact with bleach or any other sterilizer will have an effect. It is deep in the tissue. Fire blight is no a fungus, so no fungicide will have any effect. It is a bacterial blight spread by contact, frequently by bees. It can be controlled through diligent use of antibiotics, but it is really unlikely that there is anything you can do at this point that will save your plant. It is not a new thing and I remember fire blight infestations for 60 years ago and have seen it dozens of times since. I have seen it wipe out large planting of cotoneaster. I have seen it also on crab apples, pears, and hawthorns. There is quite a large list of host plants beyond these few.
Extra caution needs to be taken because it is highly spreadable by contact. Pruners are often the vector. Fire blight plants should be burned, and certainly kept away from other plants.