Possible damaged breast tissue? 😰

Here I am again.... I feel like at 4 months postpartum I still have so many questions about breastfeeding.

I was told to start hand expressing as I nurse and as I pump to increase the amount of milk I am getting.

Lately I have seen a decrease. At work I used to pump 8-9oz but now I am getting 6-7oz. I know it’s not much of a difference, but I was very consistent before.

If I have damaged my breast tissue by hand expressing, is it possible to restore that issue or is what I have done irreversible???