I came up with similar problem and the spectrum data was smilar with you. I measured the clearances and it was 12 microne above the maximum clearance valur. So that I adviced you to check bearings.
The spectrum is also showing unbalance but if there was any unbalance problem on the rotor the situation should be same as befroe but you say that it happened recently. But could you share phase angles of cross couplings and the the compressors itself. Then it will be better to determine problem whether it is unbalance or not.
Also if there is fouling or dirt on the impeller it can be another case. May be thereangular misalignment but please could you share the phaseses for all measurements.