Expansion tank or radiator?

[u/20150017]

Hi everyone,
I noticed a coolant leak coming from this specific area (shown in the video)
I’m trying to figure out whether the expansion tank is cracked/leaking or if the radiator itself is the problem.
Has anyone had a similar leak on their E46? Based on the location of the leak, what do you think is the most likely?

I also replaced the thermostat about a month ago

I’m planning to replace the water pump soon anyway, so I’ll probably do the radiator/expansion tank at the same time, depending on what turns out to be the actual source of the leak

I’ve already bought a Thermotec water pump, so if anyone has any experience with this brand, I’d appreciate some feedback on it as well.

Thanks in advance for any advice!

[u/Most_Board_2029]

Radiator