iPad Homescreen Website Links All Gray Boxes

My new iPad mini …. a few days ago I added several of my favourite websites to the homescreen via Safari’s “Add to homescreen” feature, resulting in several colourful and clickable icons with logos representative of the website and easily recognized. Yesterday I added a few more but now the new icons are all gray boxes with a single white capital letter (the first letter in the name of the site) … no colorful logos or anything. I tried adding a few that produced the correct icons a few days ago and today they produce the gray boxes. There was an iOS update between the first and second attempts so I wonder if this is the reason that the new link icons are all generic gray? Is anyone else seeing this if they have used the “Add to homescreen” function since this week’s update?