That's a bit heavy for hens, but some large breeds can get pretty hefty.
As long as your hens are active and laying eggs, they are probably okay. But let's review what you are feeding them and in what proportions. They should be getting predominantly layer or all flock feed with only very scant treats. Treats include table scraps and scratch grains. These can cause excessive weight gain and fatty deposits that can hinder long term health.
Fatty deposits can invade the liver and cause liver disease. There's no knowing what caused the death of your hen without a necropsy. If any more die, that is what I recommend.