First Grow - White Widow

nope... and i doubt you see those blemishes on newer leaf growth... those initial 1-3-5 finger leaves are more prone to blemishes in my experience and probably just genetic. Watch that internode length.. if too tight, raising light a couple inches will help nodes get a little more spacing.... or more light if it stretches too much etc etc... pictures are decieving, so don't take what i percieve too seriously.. but looks a bit tight. -- could just be that 3-finger leaf is bowing upward trying to maximize it's light, too.

No, you will harm, defoliation is for certain situations and only for FAN leaves, not sugar ones. I am a biggest fan of defoliation here 4sure, but leave girls alone !!!! You on nice path, overdoing only ruins things. Defoliation is not a MAGIC. stick for BIG harvests.

If the white is ON your leaf itself, not elevated above it, it could be powdery mildew. Take your magnifying glass and see if you notice anything directly on the leaves. If it's just a bunch of clear-ish "hairs" sticking up, those are either the start of trichomes, or trichomes that had their heads knocked off.