My best guess it's due to some weeks without hormones (other the T) pre- and post-op.
Go back on Finasteride as is often advised, if not having been at least 3 years pre-op on that stuff.
Biotin may be of some added help.
Also it is often advised to go back on Spiro (1 tab) to make up at least 3 years of that too, plus normal pre-op E.
If you have an endo, please confirm with him as he will know your history, as my take is ball-park only.
I think it is very probably hormonal drop and also op-stress related.
Take care,
Axelle