Seems to me you answered your own question. 187.5 Hz peak evident in all directions. It is ~ 7.7X running speed and, according to your own bearing frequency calculator, it is an outer race fault. I get the same result at :
You may see this frequency as a series of peaks in the higher frequency ranges which you don't show.
You would likely see this as a series of impacts if you look at the time waveform.
"How to solve the problem?" --> Change out the bearing. Confirm the outer race defect is indeed there (I would suspect a single large spall) and determine what might have caused this problem to occur (dirt, poor installation, lubrication, etc.)
Review this video from Mobius: https://www.youtube.com/watch?v=dEn2Qvh_qjc
The 2.6 mm/sec (running speed frequency) doesn't seem too high to me.
Wouldn't worry about the very low frequencies.....Likely the result of integration of your accelerometers to velocity units.
Post the results of what you find....