I'm hoping that someone can advise me urgently please.

It started with my Gander (Del Boy). First he lost the tiny feathers around his eyes so he looks like he's wearing glasses, then the tiny feathers around his beak disappeared, now under his chin is going too and one of his girls has started on the same route.

I thought it might be nutritional (I live in Northern NSW Australia - currently suffering worst drought ever - so no green whatsoever), so I bought some baby goose crumbles and give them chopped up cabbage and/or lettuce once a day.

They do live with my chooks (chickens for non-aussies :)) who are regularly checked/dusted for mites - it's impossible to keep them out as the wild birds frequently visit our orchard where my poultry run - especially in the drought as there's precious little feed in the wild atm - but I'm not sure if it's ok to dust the geese with the same stuff OR how the best way to do it would be. They are BIG birds and although hand-raised, I can't see Del Boy putting up with being tipped upside down for a dusting.

They do have a bath of water - but that only gets changed every 2 days atm (drought again, we're ALL on restrictions).

Any guidance gratefully received as I love my Geese and don't like to see them not well.