That makes sense! In my case I actually needed to turn down my iron temps for the lead-free solder, previously had it ridiculously high from when I was trying to work with the cheap no-name solder.
This new lead free stuff is great, it comes with a price tag but it’s eons better than the no-name stuff IMO.
I have flux (syringe type) but I have no idea if I’m using it correctly, or if it’s just not that great. Haven’t noticed too much of a difference when soldering with it, apart from needing to brush off the circuit board with some contact cleaner to remove the residue