Q.hibiscus
What do I do about possible root rot?
Make sure the excess water is draining from the soil and container. Soil should be moist, but never soggy.
If you think the root rot is extensive, try lifting the root ball and allowing the soil to dry. Look for mushy and soft roots and prune with a clean garden shear.
Place the plant back into an appropriate sized container, not to large.
Wait and watch for any active growth.
https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/how-to-care-for-hibiscus-plants.htm
https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/hibiscus-container-care.htm