Oh hey, how are their eyes doing? I just remembered that every time a feral or stray cat that was pretty young has had kittens near, around, or in my mother's house, their eyes get goopy. It happens most often when they are born under the house, or in the barn, but it's happened in her closet too. It's easy to gently clean their eyes with a damp rag, but if unchecked, their eyes can get infected. If you change or clean your AC filters frequently or not blast your heaters to a burning point if they are gas, it shouldn't be a problem, but I thought I should mention it as something a first time cat grandparent should know! If they look crusty or wet, you can just help momma clean them.