You have confirmed that this is a V2 version of the ARGB lights in the fan frames AND the pump motor head. My understanding of the V2 version of ARGB is that (compared to V1) it changes the way the Controller deals with several light strips connected to the SAME ARGB output port. In your system you can do this by using the duplicate connectors on each lighting header to make a "daisy chain" connection of all lights to ONE lighting header. (This does not use a lighting Splitter.) So I encourage you to look very closely inside the MSI Mystic Light tool for the many options to control the lights.
It should have separate screens for each mobo JARGB_V2 header, although it MAY show you only the headers you actually ARE using. At that level of selecting which header you are configuring there should be a choice of whether each header is handled separately, or whether all headers are to be synchronized to one pattern (from one configuration screen). THEN once you select a particular header and it shows you how many lights are present, there should be an item to choose whether all of the individual strings are lights are to be treated as one continuous string or as several (up to 4) different strings that all need to be synchronized to the SAME display pattern.) If you can tell it to treat as separate strings, that will get you the "synchronization" of three fans' displays (plus the pump top) on one JARGB_V2 header. Basically, this mode does not use that special feature of V2 and works like a V1 display would do.
If that does NOT work for you, then dwd999 has a really good idea, but it does not require SignalRGB. I think. If I understand the V2 system, that special feature is NOT applied when the light strings all are on DIFFERENT controller output ports - in your case, on different mobo JARGB_V2 headers. So if you connect the three rad fans to the three separate ports (do not use the daisy chain connection system), then in MSI Mystic Light you should see three output ports to configure, and inside each you should find the right number of LED's for ONE fan light string. So before going into configuring any of those three ports, look for how to synchronize ALL ports to one display pattern. That should get you only ONE way to configure since it will apply to all ports. Unfortunately, though, that leaves the pump lights not connected to any JARGB_V2 port. You could connect it to one of the fan lighting cables, but then that pump top and one fan would give you the same issue you started out with. That's why I suggest above that you try first to find a way to set up ONE port so it treats all four lighting units as separate units rather than as one joined-up string.