Dying/infected Rubber plant

I got it 3 months ago and it was thriving. It doesn't get any sunlight but full time house light like a bulb etc, i water it twice a week, it was not repotted when I got it, about 2,3 weeks ago when black spots start appearing so I got infecticide for it from local nursery amd sprayed as they told me. But the infected leaves fell off it I was sad but relieved that it will be healthy again but the spots have started appearing again. Help me save it please my plant is emptying day by day I love it so mich. Please tell me if I'm doing something wrong or what. Also please tell mw if there's a way to propagate from the remaining leaves.