Humidity levels seedlings to flip

[PokerJay83]

First time growing. Got 4 in seedling running a 40-45% humidity on day 5. I have an intake/exhaust fan that I can take and put in window. If I leave intake on I can get the RH up to 55-65, but after removing fan it goes back to 42 or so within an hour.

What is the ideal RH at this stage, and if needed how could I increase RH after flip? What is ideal RH in flower?

 

[Dirtbag]

Seedlings and vegging plants I like around 65-70%, transition to flower around 60-65%, mid flower 45-50%, late flower 35-40%. But I vape sulphur in veg. The closer to 70% in veg the better imho, but without sulphur I'd keep it closer to 65%.