Sudden death gosling

[Mbeck09]

Hello,
Have a goose hen that successfully hatched 3 goslings about 2 weeks ago. All 3 we're doing great, acting perfectly normal yesterday.
Today I noticed that 1 was missing. Found the gosling dead in the yard. Other 2 we're normal this morning.
This afternoon 2nd was missing, found dead by the barn.
Neither gosling has any signs of trauma, appears as though they just died.
3rd appears to be normal at this time.
Geese are free range with access to barn, chicken layer pellets and occasional cracked corn.
Any ideas why the goslings died?

 

[Goosebaby]

They could have choked if the corn is too big, I’m really concerned about the layer pellets, young birds and males of any age don’t need the levels of calcium that layers need, it’s to hard on their kidneys. Goslings also need extra B vitamins, especially niacin, which any feed formulated for chickens doesn’t have, they also need more protein as they’re growing, which a layer feed doesn’t have.