Case Fans Slow On Startup

I noticed my fans don’t all start at the same time when I power on my PC.

•	AIO fans + rear exhaust: turn on instantly

•	3 side intake + 1 bottom intake: start about 2–3 seconds later

All intake fans are connected to a fan hub, while the AIO and rear fan are connected directly.

Is this just the fan hub taking a second to power up or get a PWM signal, or could it indicate an issue?

Everything works fine after startup — just curious if this is normal.