Definitely not unusual for the amount to drop - my teens have all dropped stuff the past few years.
Last year (y13) DD1 volunteered at Rainbows (1hr) and Brownies (1.5hrs), did two one hour blocks of street dance, and played in the school orchestra and her school’s sixth form netball team. She was also her school’s deputy head girl and had a part time job which gave her 3-15 hours depending on the week (30 in school holidays), but this was still a huge drop from when she was younger - she did cross country, triathlons, diving, rowing, drama...
DD2 is 16 (year 12) and over the years has dropped cross country, drama, netball, gymnastics, triathlon. She now just does dance - CAT scheme (10 hours a week of contemporary and ballet), plus 3 one hour sessions of street dance. She works on the desk/teaching and choreographing at the street dance studio the two nights she’s there as well so it does take up the full evening.
DD3 is 14 (year 10) and dives semi seriously (16 hours a week). Recently dropped a lot too - football, netball, cross country, swimming, trampolining, triathlon.