I have been using a lot of PETG in the last few days but I switched to PLA yesterday, and ever since I keep seeing remnants of PETG in the "custom first set of a print (the two lines)
Is there a way to purge/ clean the toolhead (I suppose it’s happening there) from all finally?
What you want is typically called a “cold pull”. That is also the way to go for removing partial clogs of the nozzle. I think Bambu have in the Wiki too.
The question might be if PLA decomposes at 245 or not. If not, just manually raise the extruder temperature to 245 and hit the extrude key about 10 times.
That looks strange. Is it underextrusion? Maybe you still have a serious clog? If you have a spare nozzle, you could try swapping to see if the problem is in the nozzle. Alternatively, there could be something stuck in the extruder.