What is this leak? M54 2.5i

[2one3E90]

I left the car parked for a week and half. Before I left it, i topped up with distilled water. Now I come back and see this. This is my coolant level also. I have done Valve cover gasket and oil filter housing gasket 2 months ago. Oil pan is a little bit but it might have been from the oil filter housing gasket. What hose is leaking or is it radiatior? The car hasnt been driven in a week or 2.

[Clearancediver]

Expansion tank is exactly that… as coolant heats up it expands…. As it cools it contracts and draws from the expansion tank…

Also… you top up with a mixture of distilled water and antifreeze… as specified. Usually a 50/50 mixture. If you top up with distilled water only you lower the boil point of the mixture which causes overheating etc at a point when the radiator antifreeze mixture becomes too diluted by only adding distilled water ….

[vt100]

what color is the liquid?

[pungo]

Hard to tell what's going on from those pics
Completely clean the area where it's leaking, then take some better pics where the leak is starting.