This Hibiscus plant is indoors for the winter and outdoors for the summer. This summer was its best ever with hundreds of blooms and more than doubled in size. Brought back inside in mid-September and after a couple weeks the leaves would turn yellow and fall off. I noticed some fine webs (spidermits?) on it, so I sprayed a few treatments of End All II. Its been over a month since I last sprayed and the plant continues to loose leaves, they either turn yellow/ dry up and fall off, or green leaves just wilt, dry up and fall off. Now some branches are drying up and breaking off. Gets regular watering and soil is not allowed to dry up. Any ideas? See attached pictures
Hibiscus can be quite temperamental when you change their conditions suddenly (such as by bringing them indoors when they'd been outdoors, watering them inconsistently, exposing them to temperature swings, etc). The good news is they typically recover from all of those things. I wouldn't have been at all surprised for your plant to go through a phase like that when you first brought it in, but since it's been several months and it's still doing it, it makes me think that there's still something that's off. I'd definitely check on your watering--they don't like to dry out too much, but it is possible to overwater them and since they're indoors they won't need to be watered nearly as often as they did when outdoors so that would be one possibility. Also, I would check to make sure that the plant isn't in the direct path of air from a heating vent, and that it's not catching cold drafts (either from being too close to a window that's not sealed 100%, or if it's near a door that gets opened regularly letting cold air from outside into the house, etc). Also, if it had a spider mite infestation any leaves that the mites damaged before you killed them could continue to die off--damage from things like that often looks worse even after you thought you fixed the problem because the mites had done enough damage to kill the leaves, but the leaves hadn't actually died yet. Then a few weeks after you think you get rid of the problem, the leaves end up dying from the damage that had been done weeks earlier. Spider mites are also tricky to get rid of and it typically takes multiple applications of whatever product you use to get rid of them (and you need to make sure and get it on the underside of the leaves which is where they live) so I'd also consider the possibility that you didn't quite get rid of your infestation.
I would not water them as much as you are. Let them get dry between waterings. Since they're not outside, blooming and growing, they don't need as much water and they hate wet feet.
Also, keeping them moist creates the conditions spider mites like.
When you said the leaves were falling off I thought, well that's normal when you bring them in. But the dying stems aren't. That's why I'm 90% sure you're watering too much. I have killed many hibiscus over the Winter by over watering. So, when you think they need water, wait. I bought a moisture sensor and only water when the soil deep in the pot is dry.