Hello Monntricia, looking at your E. Black Prince, to me it looks like it is getting overwatered. It is a bit worrisome when the inner leaves like that are getting black patches. Try to keep it warm and dry for now, if you can. Twice a week is too much, if grown indoors, and if you do have to water, water directly the soil, and try to avoid the leaves. It is different when it is grown outdoors where there is much more airflow around the plant that helps in dry out time and good active gas exchange at night when their stomates are actually open. With the changing seasons, you have to adjust watering, scale it back, media takes much longer to dry.
As for your jade, it reminds me more of a variegated Portulacaria Afra with its reddish stem. Anyways, they have similar attributes growing wise. They go into a cycle of dropping its oldest or the lower leaves, as it redirects its energies to newer ones that will grow either from the topmost part or at any node of the stem. So do not be tempted to overwater. Water only as needed. They do make active growing when temps are cooler, but it will first manifest that leaf dry out. Again with the changing seasons, adjust and scale back watering. In my area I grow them outdoors but our winters are milder, and it gets watered as Mother Nature sees fit.
