You've definitely done a pretty good job for your first grow, they look great.
They don't really look like they need to lose any leaves tho, so I wouldn't defoliate if I were you. Especially not a "bigger defoliation". If you have to do it, take a single leaf, once every day, preferably every second day.. I'd recommend just letting them grow as is tho, unless they start to grow a bunch of new fan leaves suddenly.