They are either the Fungus Gnat or Shore Fly. Try changing the soil using a sanitized media. By all means, avoid overwatering. The leaves are falling off my rubber tree from the bottom-up. My plant has cotton-like spots on the underside of leaves.
Mealybugs are the culprits.
First try using a strong stream of water to wash off as many as possible. Then, if needed, apply pesticide and soil systemics. Make pesticide applications at 7 to 10 day intervals. Systemics 2 to 3 week intervals. To become a Master Gardener, you must attend an intensive, multi-session training program and carry out 60 hours of volunteer activities.