Mmm Rh & bud rot ah...
From what i understand / read the spores of botrytis also known as bud rot /grey mold start to take effect around mid flowering & only really showing effect or results in the last couple or so weeks of flowering.
Now prevention is the best option as the rot loves high RH & low temps aka low temps holds more moisture in the air so this may lead to point of intake source of air etc or where it is coming from & what conditions it is sourced from ! plus over all difference of temp between lights on or off.
Ideally 5c difference between the two is pretty good but can get away several C difference but not much greater than beyond 10c.
I keep a base line temp of 20c lights off as best as i can on average lights on 27c but this may change a little during summer months when warm days may spike stuff but not a great problem.
Watering is another issue but best done when lights come on so excess moisture can be burnt off during the lights on period... so timing of watering is essential with some hydroponic systems as you don't want a saturated medium when lights go off which may spike RH to unsuitable levels.
I just think of it as a little puzzle to solve 'n' work out perhaps a slight change may be needed to avoid the rot given a basic guide line on how it may manifest a tweak here or there to sort it out perhaps !
On a side note i do run a dehumidifier during lights off as that is when most of the time the RH spikes in less ya in very dry part of the world... it gets turn off when lights are on when most of time the RH is lower in that period but the dehumidifier has treated a larger enough volume of air in that period to deal with stuff, but based on a passive intake tent.
Just an individual set up really & our conditions may change stuff
