Have you considered that as he is maturing, he needs to potty less often?
I'm finding that with Callan. I used to find he was good for 4 poops per day. Now we seem to be down to 2, sometimes 3, but difficult to predict except for the morning. That's a given. I take him out probably 6 times per day, either in the backyard or walks. He will pee everytime, just because.....but poo, not so much.
Indy only poos once per day, rarely twice (usually at the cottage when he is running around more)
I don't think you said he was having accidents in the house? If not, don't worry about it. Just take him out on a regular schedule and he'll be fine.
Also, Callan will not do his business on a leash. I finally got him to it once this week. I didn't train him to do it, so he doesn't get it. Hopefully, I've now passed this hurdle.