I remember reading that fire shrimp can potentially eat berghia nudibranchs(I might be wrong).
But I've had multiple experiences with using berghia nudibranchs, all very good to the point where I would sell all of the extras locally for profit. In my main display, the nudibranchs will usually get rid of them, but after a year or two they'll come back again, which is unfortunately why I don't keep wrasses.
TBH if you put them in August and you don't see a change in your aptasia problem, they are probably gone. Usually my aptasia is gone within 2-3 months of adding 8-10 nudibranchs in my 230 g. I also will only add them into the tank if there is like an uncountable amount of aptasia.