Rubber plants are used to growing towards the light and will shed lower leaves as they age. Just like any other palnt. These things grow low down in tropical places.
It shouldn't have needed feeding in 'new' compost. But,maybe it had been starving well before you noticed the lower leaves. I wouldn't feed it too often. Once a fortnight is enough during the growing season.
Keep it moist - but not too wet. Soak it, drain it and forget it for a couple of weeks. Spray it with mist every day if it's in a dry place.
Give it a real treat and wipe it's upper leaf surfaces with a cotton ball soaked in milk - gets the dirt off and makes then shine. Wipe with plain water on the underside.
Did you move it from it's original position? It needs light but not direct light, I think.
Scuzz P. Thrower.
Time I went on holiday, I think >