The fabric pot shouldnβt be bleeding out soil, at least definitely not to an extent where half the contents are gone through drainage. The only explanation I can think of is you left the soil really really loose when transplanting into the pot and the water just reduced the contents to what it should be.
Did you lightly pack the soil? I usually use like a one gallon pot filled with some soil and use itβs natural weight to gently pack the soil a bit so you donβt get that sinking effect, but it isnβt packed so tightly your roots wonβt spread and breath.
I donβt think adding soil is the end of the world provided your not burying any stems growing out from the main.
If your that far into flower you may just wanna bite the bullet on it. I doubt the soil will get any lower if compacting was your issue, and the roots are pretty much done development at this point so they wonβt be looking to spread much if at all as far as I know.
Either way will be fine imo. Just if you wanna use your resources.