Generally, they are looking at things at a larger scale than you are and making ethical decisions in response to the way the farming industry and large scale food supply operate.
On your scale, what became of your hens' brothers? Why no sons? More broadly, there wouldn't be ex-farm hens like yours, if the farms, or the particular methods of farming, did not exist. Someone who campaigns through their actions for the end of the egg industry is not faced (in a logical sense) with questions about what should happen to the by-products of that industry ('elderly' hens), that's an ethical question for egg farmers and consumers.
So it makes sense for people like you, who are inclined to eat eggs, to get those eggs in the way you do, giving longer life to commercially unviable old hens. It's the other egg-eaters it would make most sense to talk to, if you wished to expand this practice - and reduce commercial egg production slightly, as they wouldn't be buying so many farmed ones.
If one objects to animals being killed in order to supply one's food, then eggs and milk are out, as the male offspring are killed, as are the older females, when productivity declines. Killing is inherent in the dairy and egg industries. The killing can be viewed and rejected as unnecessary, by rejecting these foods as unnecessary to humans.
If one objects to the idea of taking from animals what is theirs, or produced to feed their offspring then, self-explanatory.
Bees - the 'stealing' argument and, some commercial producers apparently kill and re-stock each year, rather than pay to feed over winter.
It's wild bees - many different species - that are declining so worryingly. Commercial honey bees do face their own problems but are not the main concern re 'the decline of the bees'.
Sheep - stealing and, how do you distinguish wool derived from live sheep from the wool taken from slaughtered sheep? Some wool is a product of killing, some killing is a part of wool production - unless you let your sheep die of old age, which isn't generally the practice in commercial farming. So, object to killing animals? Might avoid new wool.
There may be welfare arguments with sheep, as well as other animals, too. So a desire not to support, with ones money, an industry that transports animals to slaughter in big lorries or treats them in certain ways e.g. Docking tails from sheep, all sorts of concerns with other animals.
Then there are environmental arguments about the inefficiency of supporting human nutrition through animal production, versus plant-based food. Complicated at the specific level, as some land is more suited to some types of production than others, some plants more nutritious to animals than people, some kinds of production more inefficient and damaging than others. But, at the large scale, pretty irrefutible.
So, killing, welfare, stealing and environmental concerns are the main issues I'm aware of. Different vegans will be more or less motivated by different issues, so may make slightly different choices.