Humidity spike?

that's actually the humidity you should be growing at during this stage of the plant's life, the 60%, not the 40% Rh, 40% at this stage would be considered over transpiration and if the plants transpire too much then they wont grow as much. In relation to the spike idk man, it could even be a result of their transpiration going too hard and they end up making the whole tent's humidity go up. it could also be a fan malfunction, a timer malfunction, it could be that the place where you are pulling air from the outside is a spot where humidity gathers during the peak of the day.... lots of things it could be, but sure as hell whatever did it took your humidity levels to the right ones. stay lit growmie. i experienced similar stuff but only during the night, without a dehumidifier it would go up to 99%Rh everynight, but if its only during the night it doesn't really hurt the plant as she is resting, other than to provide a possibility for fungus to settle in during the night.