4 Circle lights parallel to each other flying very slowly

I Came Out My Backdoor looked up noticed large circular lights flying overhead like in a square formation right over my tree in my backyard about Treetop level. It was silent.. I ran to get my husband in his building and by the time he came out it had traveled about 100 feet in about a minute time. He came out and saw four circular lights no light shining down but there were huge whitish-blue bright light circles in square formation. It continued flying about 400 feet to where it was out of sight over trees in our backyard.