Q.potted hibiscus plants
I have several plants that are putting out many yellow leaves and the green leaves and blossoms are
very tight and knotted with what looks like white foam on them . I don’t want to loose them but they are not looking good. I can’t upload any pictures at this time.

This could be Mealybug on your plants.
Treat the plants with Neem Oil.
Here are some links with more information.
https://www.gardeningknowhow.com/plant-problems/pests/insects/mealybugs-control.htm
https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/hibiscus-sticky-leaves.htm
https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/answers-to-what-causes-hibiscus-leaves-turning-yellow.htm
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm