I have a 2 yr electrical degree and when I worked for Lucent technologies many moons ago we used the adjustable wellers... We set at 650F. We were soldering laser diodes, VSB's and surface mount repairs. Even when I worked for apple computer in the 80's doing componant level repair with chips and through hole we did the same..
Flux is you friend and makes the solder flow. Flux and tin the tip before turning off gun. ( Load tip with glob of solder)
My two personal guns are 20 years old or more. Never replaced tips yet.
I use these with digital readout..
I say your running too hot.
And soldering outside in a wind cools the tip too much... I often have issues and need to turn up temp some...
Of course I have older models...
https://www.amazon.com/Weller-WESD51-Digital-Soldering-Station/dp/B000ARU9PO