I had tiny white insects (whiteflies) on my hibiscus leaves. I washed them with a solution of 40 parts water to one part soap. I seem to have gotten rid of them but I notice that the leaves are now very shiny (but not sticky). I am concerned that this might be another insect infestation. What should I do? The plant is currently sitting in an east facing window.
Thank you so much for asking your question about white flies on your hibiscus of the Toronto Master Gardeners. My short answer is that it sounds as though you have got on top of your white fly problem, but since we all have a bit of time on our hands, why don’t you take a wet cloth, dipped in a light solution of dish washing liquid and warm water, and wash each of the leaves. That will definitely clean them. I also suggest that you could take the plant outside to give it some fresh air this warm weekend and let nature wash the plant, give it air circulation with the breeze, and maybe expose it to some wasps that will put paid to the white fly. For your interest, there is more on white fly control at this website:
http://ipm.ucanr.edu/PMG/PESTNOTES/pn7401.html
I am copying below a past answer to this website on hibiscuses that will also give you some more information on growing a really healthy plant:
Hibiscus are spectacular when bursting with bloom, but many times we hear from gardeners that their plant, although healthy, is not producing the number of flowers expected. One of the main reasons for this often is the amount of light your plant is getting. In order to flower abundantly your Hibiscus requires at least 6 hours of direct light per day. Your plant can certainly survive with less, but it will not produce many flowers.
Hibiscus also requires good rich soil, moist – but not soggy. You may wish to check the soil medium in which your Hibiscus is planted to make sure that is draining properly. These plants suffer if left in soggy soil, rot can quickly set in and one of the first signs is buds dropping. Lack of fertilizer may also be the reason for the lack of flowers. Is your plant in a container? If so, you will need to feed your plant as the potting soil does not have the nutrients needed for bloom. Look for a balanced fertilizer and make sure you do not over fertilize as this will burn your plant. Kelp meal is a good organic fertilizer to encourage blooming in Hibiscus.
Buds dropping from Hibiscus is often caused by thrips, but if you have checked and saw so sign of these pests, you need not worry.
I am attaching a link to a site that will give you more information on successfully growing Hibiscus.
https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/light-requirements-for-hibiscus.htm