First, how are your four fans connected? I am presuming that all four of these are used for case ventilation - that is, none of them is used on your CPU as its cooler. But your mobo has only ONE CHA_FAN header, so connecting four fans to that would require that you use a Splitter system for four fans. I ask because the easy way to connect four such fans in your system would be NOT to connect to the CHA_FAN header, but to connect them instead directly to a PSU power output. IF that's what you have, then your mobo has no way to control them at all.
Now, there IS a way to get control, even if you don't have them connected that way now. First, a "rule of thumb": virtually any mobo fan header can supply up to 1.0 A max total current to all fans connected to it, so you need to verify the max current draw spec for each fan. In your case, the specs are 0.13 to 0.18 A max per fan, so a total of about 0.6 A max - OK for connecting them all to a single header. To do that you need a Splitter, NOT a HUB. (A Hub is a different device and really can be used only with 4-pin fan systems.) A Splitter has one input "arm" ending in a female (with holes) fan connector to plug into the mobo CHA_FAN header, and two (or more) male (with pins) output connectors to plug in your fans. A HUB, on the other hand, has one additional type or "arm" that must plug into a SATA or 4-pin Molex power output from the PSU, and you do NOT want one of those. Few Splitters come with four outputs, but some do and you can create one easily. Also note that the Splitter can be either a 3-pin or 4-pin type because a 3-pin fan WILL plug into a 4-pin male connector and work if the header sends out the correct signals. So, you can get a Splitter like this that looks like a small printed circuit board, and you just have to secure it properly so it does not short out to something
https://www.newegg.com/black-en-labs-30cm-cable-splitters/p/1W7-0053-00001?Description=fan splitter&cm_re=fan_splitter--9SIACJF5528562--Product
Although that unit has one of its outputs labelled for the CPU, ignore that (see later).
As an alternative, you can buy three common 2-output Splitters like this (3-pin model here, but 4-pin one would also work))
https://www.newegg.com/p/N82E16812423168?Description=fan splitter&cm_re=fan_splitter--12-423-168--Product
Plug two of them into the outputs of the third to make a "stack" that converts one mobo header into four outputs for your fans.
In using Splitters you need to remember a little detail. Any mobo header can accept the speed signal sent back to it from ONE fan for counting and display; it also monitors that signal for fan failure. But it gets totally confused if fed more than one signal, so any decent Splitter will only send back one, and ignore the speed signal of the others. When you use Splitters, only ONE fan's signal will be displayed and monitored for failure, and all the others on that Splitter system ignored - you'll never "see" them. But that has NO impact on ability to control speeds. It only means that YOU should check all those fans from time to time to be sure they all are still working. In the case of the 4-output board model, the only output connection that does end back that fan's speed signal is the one marked "CPU", but when you use it for a group of case vent fans just ignore that label.
So, with a Splitter system and four fans connected together, plug the Splitter input arm into your mobo's CHA_FAN header. Now to configure that header in BIOS Setup. Go to this web page for your mobo
www.asus.com
Click on "Support" at top right, then on "Manual & Document", and download the correct version - I got the English User's Manual
https://dlcdnets.asus.com/pub/ASUS/...27.456572294.1558709797-1856104645.1502368712
See p. 2-8. It says to push the "Del" key during the initial POST screen displays. I prefer to hold that "Del" key down until the opening screen of BIOS Setup appears - see p. 2-7. Use the F7 key to toggle between EZ Mode and Advanced Mode, and go to Advanced Mode (p. 2-8), then choose Monitor from the top menu bar. See p. 2-32 to -34. Set the CHA_FAN configuration to: Chassis Q-Fan Control to Enabled, Chassis Fan Profile to Standard, and if necessary Chassis Fan Low Speed Limit to a suitable value. (Default is 600 RPM, but your fans MAY be able to run slower at minimum before stalling.) Use the Esc key to return to the main menu, then choose the Exit button at top right. See p. 2-42. There Choose "Save Changes and Reset" to save your settings and reboot.
On p.1-16, item 6, the labels on the CHA_FAN header lead me to believe that that header can only use the older Voltage Control Mode which is necessary for control of 3-pin fans, so this configuration should put all four of your fans under automatic speed control based on the temperature sensor built into the mobo. To verify it's working, do this simple check. The normal process when you system first starts up is that all the fans start at full speed for a few seconds at most as the POST process proceeds. But then the system detects that it is cool and slows down the fans. So, open your case when the system is off. Push the front Power button and watch the fans carefully. If they all come on fast, then slow down after a few seconds, then your system IS controlling their speeds properly.