its not possible for them to die off. our bac threads cover how they self feed. all they need is submersion time.
technically its been long enough now with the boosters used, if you did the full water change it can handle some bioload we like to start with.
since you are in no rush, 30 days is the correct time for you to wait after adding any ammonia, and any bottled bac, even if you just did it once totally against the directions on the bottle
regardless of whether or not you tested anymore, or added anything whatsoever other than water. you are too far in to stop cycling in other words. 30 days, done, no need to even test further. change out most or all of the old water before you start your system w some corals
qt all fish, easy easy.