Yes to the osmocote.
It looks like a root problem. Some nurseries over water. The plants either get used to that daily watering routine, they need it because they are root bound or they rot the roots from being constantly soaking wet. One sign that this is going on is if the inside of the plant near the crown has a lot of dead, black, hanging leaves. The top of the plant may still look good or salvageable.
What I do in this case is dig it up and separate the good from the bad. If the stems still look ok, you may get it to bud up so leave that if the root is good.
So it appears that you do have some buds coming back so that is good. Part of the plant should recover. You may end up with a few smaller plants.
