Melon stems don't update observers when they produce a melon

So when a melon pr pumpkin produces a melon/pumpkin, an observer won't detect the melon from the melon's original stem. An observer placed in front of a melon/pumpkin stem will detect when a juvenile melon/pumpkin stem grows from 1 stage to the next but won't detect when an adult stem produces a melon/pumpkin.