Distinguishing Toulouse goslings those with dewlaps from those without dewlaps

[Svett]

Hi there I need help my lovely people. This spring I bought Toulouse geese 4 dewlap ones and 4 without dewlaps. During the spring I kept them separate in order to control the breeding but a week ago I have noticed that they have started mating and laying eggs. The trouble is they are all together and I have lost the track who is mating with whom but they are all at it.

I have only managed to get one dewlap Toulouse gosling this spring out of 40 eggs but 4 Toulouse goslings without dewlaps. I was not able to distinguish them until they grew up a bit and the one started developing dewlap. She is now fully grown up, totally adorable and still loves me.
As I am planning to hatch the eggs they have laid in autumn and as I have no idea who are the parents I would need some help in distinguishing the goslings and determining which one is dewlap Toulouse. This spring I was not able to distinguish them at all. Please help…

 

[Svett]

Forgot to mention I plan to give away gosling which will hatch but would like to keep dewlap ones hence I need some way of telling them apart.