Adorable!
Unfortunately they’re too old to be sexed. You can vent sex them fairly easily when they’re only days old, as they get bigger and squirmier it gets harder. Once they’re adults you can start making guesses based on behavior and sometimes body type. Ganders tend to have longer necks in proportion to their bodies compared to females, ganders will also tend to want to get in between who they’ve bonded with and “others.”
Things can get confusing if you have multiple ganders as ganders will often bond and get protective of other ganders.
You can also have them dna sexed.