Using a Splitter does NOT impact your ability to control the speed of the fans - they all will be under mobo control. To do the three on one header, you may need to 'stack' two simple two-output Splitters, and maybe that is exactly what you have done. So split them up as three on one header, and two on another. OP, you have a mobo now with TWO CHA_FAN headers, and five 3-pin fans in total. That type uses more current - can max out over 0.4 A. Be wary of what are called 'LED fans' - they are the early lighted fans with only one cable from fan to header, and they show only one colour all the time and you have no control over its brightness. In fact, more than that might be possible IF you know the max current spec of each fan you are using.

Now, most current case fans pull 0.1 to 0.25 A max, so three on one header using a Splitter normally is NO problem. However, when you use a Splitter, you are limited to at most 1.0 A max current for the entire load on that header. That way the header delivers the same varying voltage to all the fans on the Splitter, whereas most HUBS do things differently and can NOT contol the speed of 3-pin fans. A Splitter is the right way to connect several THREE-pin fans to a single mobo header.

Pc fan hub