Hello, William.

Tropical hibiscus guidelines differ from those for hardy hibiscus (bushes that come up every year) so the following message offers tips specifically for your species.

 - Yellowing tropical hibiscus leaves typically indicate water issues.

 - While tropical hibiscus appreciate moist soil, take care not to overwater.

 - If you think overwatering could be the case, allow the soil to dry out a little, then check for dampness before watering again.

Be sure to keep the pot in a warm, sunny spot. You might consider extending its hours of sunlight until closer to noon to allow soil to dry out more between waterings. Close attention may be needed until this current heat wave passes.

Your tropical hibiscus will flourish in its pot and can be brought into the house for the winter if you choose to do so. Just be sure it has a bright space with plenty of sunlight.

Additional information on caring for your hibiscus is given here:

https://gardens.si.edu/learn/educational-resources/plant-care-sheets/care-of-hibiscus-rosa-sinensis/

https://yardandgarden.extension.iastate.edu/how-to/hibiscus-iowa-gardens

We hope this information is useful. Your additional questions are always welcome.

Wishing healing for your wife and good health to you both,