I'm no expert, so take this with a grain of salt.
Just like humans, rats have their own personalities and moods. They may be in the mood for something one day and not so much another time. If it's consistent, then it may be worth worrying about.
But I'm going to go into scary territory. Don't take this to mean that there is something wrong with your rat. In my limited experience, your rat still sounds fine. He's licking and grooming. My first rat death was with my first rat after 3 days. She suffered an URI, which I probably could have caught if I was more aware. I knew that rats sneezed a lot when moving to a new place, but I didn't know how much, so I didn't catch this URI in time. What clued me into her health problem was her behavior. She became sluggish. I noticed that there were fecal stains on her backside. Now that I've had rats for 3 months, I know just how clean those normally are. Chloe was not grooming like she used to. She was so sluggish that when I had her on the table, she weakly sidled over to the edge and fell off. Fortunately I was there to catch her.
So I'm trying not to scare you. Like I said, it doesn't sound like Ashe is exhibiting the same sluggishness that overtook Chloe before she died. He's grooming himself, which is more than I can say about Chloe. It sounds like he's being a normal rat right now. He may perk up and become friendly again. Sometimes a rat just wants alone time. I hope that's your case, but keep an eye out to see if he continues to be as sluggish. My rats haven't reached 5 months of age yet, but I imagine that rats are still pretty lively around that age. One of my rats is more reserved, and she sometimes will stay in a corner, but even she will sometimes approach my hands to lick them.