Hello Seedhunter, what is your watering regimen for your plant. As mentioned by Sue it does like lots of full sun and alongside with this it likes lots of water, and good humidity levels especially during summer time when it should be actively growing. Full sun outdoors is much stronger light than sun coming indoors. I would put that plant outdoors maybe in part sun to acclimate then slowly into more sun while light levels are still strong, before Fall season ensues further.
The plant looks in too much distress, and fertilizers at this point will just aggravate its situation. Scale down or stop the fertilizers for now and concentrate on reviving the overall conditions of the plant.
It is not a lost cause yet, I still see lots of green on the trunk, so just try to improve its light and watering needs. It can still bounce back.
