I think it’s fine amigo.. keep in mind you just flipped to 12/12 and it has signaled the plant to switch to an entirely different agenda than vegetative growth.. you will start seeing growth shift and not be the same it has been in the weeks before. Some excess and deficiencies can have the symptom of thin leaves like emeraldLake said, but if you’re pretty confident you’ve been doing everything right, it’s probably just the shift to flower.
Good luck!