Coolant leak underneath the car coming off the oil (pan?) area passenger side.

What is your question?

Recent work done: 1. Fixed radiator hose leak from the OEM nipple on the driver side. (new hose attached) 2. Coolant Expansion Tank upper nipple ruptured at the connection between the tank and the hose. Replaced tank and re-attached hoses. 3. Re-filled with coolant and noticed there is a leak underneath the car passenger side dripping "off" the oil pan area" (ONLY when the engine is running) - NO LEAKS when the engine is off or even while the car has been left sitting for a while. I'm not sure what to do / repair or if I should take it to the mechanic. Any advise would be great!