Why did my male cockatiel stop talking and whistling after a year of constant mimicking?

My bird learned phrases and songs very quickly and would whistle and talk frequently through out the day. He spends the day on top of his cage at a window in my art studio with many items to keep him busy playing, including mirrors. He usually would talk freely looking at a mirror but no longer does this. He would also show off every time he was with me in the bathroom on the counter top. When I took him out on our patio he would strut and show off but now only cheeps, no mimicing. He also would always talk when in my car, no longer does this either. Today when outside washing my car, I put him on our iron gate nearby and he did start whistling and saying usual phrases for a few minutes. I know he has now reached his male maturity but would this cause such a drastic change? We did travel in our motor home with him for two months and he appreared to love living on our large dashboard by the huge window. Could change back to the studio be causing this? Still hops on my finger.

If anything, reaching maturity should have made him more talkitive, not less.

I would go to the vet for a check up. Birds will hide illness from the most beloved people, and sudden changes in behavior could mean illness.

Ghost Adventures Bird cage Theater part 1 of 5