Thanks for the compliment TK!
Phoebe is correct that there is no cause for alarm. Jade plants
can support only a limited number of leaves at any one time. Increasing the light will increase the number that it can support. The plant
sacrifices older leaves so that it can continue to produce new leaves.
You can remedy this by increasing the light or by periodically pruning back some of the longer stems. Pruning will help maintain the compactness of the plant
and keep the center from becoming too sparse.
Of course, you can also do nothing.