Did it get nipped by cold weather before you brought it in?
Does not look like any insect related problem. Could be fungal related. You might try one of the triple cides that take care of insects, mites and fungus. It won't hurt. I use GardenSafe Fungicide 3.
Were you/are you watering it adequately? My Oleander sucks up water fast.
And yeah - the Epson Salts might help - cannot hurt. During the regular growing season, I give most everything a shot of Epsom Salts periodically. (Rose love it and my Brugmansia certainly appears to respond well.)
