I had two incidents that my tensioner making lord noise in cold start after 50k miles and I had to remove a lot of things to remove the bottom cover. Someone in here recommended to cut the cover open for easy tensioner replacement if it’s making loud noise too early and recommended aluminum tape to cover it up.Those pulleys do not look good. I don't remember any of mine looking similar after both TBs I did. They were always clean. I wonder if your engine was overheating which caused some rubber melting and embedding onto the pulleys.
Also, can you explain why you had to cut out the covers for the tensioner replacement? You need to take the covers off to replace the belt and pulleys anyway. What was the purpose of the cutout? Did you seal it with anything? I would think dust and dirt constantly getting inside is not a great idea for those components.