The leaves are sweating. It’s a natural part of the respiration cycle.
You will get that where your leaves overlap as well. I move my canopy about and target where the leaves touch as it could become a hot spot for mould
Keep exhaust fan on and a circulating fan moving air over the plants
Thank you all
Like @Davyg says. I have had the same thing happen. Leaves touch each other / overlap and would be more noticeable if I moved a fan or forgot to turn it back on. Transpiration is what makes the plants engine.
If you seal a leaf in a plastic bag you can really see how much moisture it releases by the amount of condensate in the baggy.