Taking advantage of PRFPMI data taken yesterday, which can be identified with the relevant Guardian state (Fig. 1), I roughly and easily checked coherence among DARM, MICH, and PRCL (actually, I am not sure there are proper channels to be seen; I firstly tried to see K1:LSC-DARM2_OUT_DQ or so, but no such DQ ch names were found....) as in Fig. 2.

Some peak structures have large coherence, so we may be able to reduce these noise by modifing MICH or PRCL control or some relevant ways.

Interestingly, NAB PDs have coherence with DARM, but unfortunately, the NAB PDs are not of DQ, so I can only check below a few Hz (Fig. 3). Anyway this coherence may be due to alignment-wise coupling to the intra-cavity power...??

More detailed checking should be done with more systematic way, like using bruco. Please have a try!