I've found that all varieties of hibiscus are pretty darn resilient with TLC and patience. If you suspect an infestation, identify the culprit first. Different methods can be used on different 'critters'. Personally, I have fought aphids numerous times on my plants. I grow weary of their constant attempt to 'sap' my blooms. But lets get back to your problem. From the information I have gathered, you recently moved your plants inside? A change of environment causes stress and this causes yellow leaves. Were the plants up-rooted and placed in pots (stress x2)? Aphids usually do not cause serious leaf and bud drop. These little creatures are found at tips where buds are. They are tiny pin head sized bugs that are colored black/green/red/ etc... that coat new growth. There are different methods to counter act them, but I suspect your problem is different and most likely environmental. Is there any way you can upload some images? Or even email me directly? Hope this helps.
Ed

Here is a link that might be useful: Yay, bugs

S544 - you bought them in summer '12 or '11? Have you confirmed an insect infestation? Don't use dishsoap/ laundry detergent/liquid handsoap ..... more on that later if you decide you want to open a dialog.

"A change of environment" doesn't necessarily cause stress, but 'certain types' of changes CAN ..... and stress is not necessarily made manifest in chlorotic foliage.

Highest on my list of suspects for the leaf abscission/aborted buds are:

Over-watering
Tight roots
Using a high-P fertilizer
The recent reduction in photo-intensity coupled with natural decreasing photo-period (technically, it's the increasing dark period, not shorter days, that would be the issue if it is indeed photo-period related).

Al