Help interpreting the FBA results

Dear experts,

I followed the FBA tutorial and finished with my single shell data (30 b=1000, 3 b0). Then I used TractSeg to get the fixel mask of 72 tracts and extracted the significant fixel numbers of each tract.

To my surprise, compared to healthy controls, I observed decreased FD at some tracts in patients, but FC and FDC didn’t vary. Is this reasonable?

Best wishes,
Yuting