I need some help please. I’ve had a Rex begonia for a couple of years that had been doing really well until lately. It’s looking kinda tired and worn out. The rhizomes have grown very long and leggy and have grown out of the soil. Do I need to repot it and if so, do I plant the rhizome necks under the soil? This is my only begonia so I’m a bit lost on what to do and haven’t been able to find any guidance on this particular problem. Thank you for any guidance!!