You coulda spent $20 and got a hollow-core door to hang and ran the ventilation through that out a window or into a nearby bathroom vent. If you run an intake at floor level you'll get cooler air so you won't need to use that crack to blow air in with that fan which I'm sure takes up a lot of...
I heard you can just add a drain :O If you're gonna DIY go aero tho, lots better
As for reflectors... if you're DIYing one you're prolly not worried about perfect math, but just making sure light gets focused on the plant area. I'm sure you could design an awesome sphere to keep the lights...
Would rather lose a little light than burn my plants. People grow fine with CFL so if u got a HPS, nothing to worry about. Me, I'd cut into a door and just make ventilation in it since hollow core doors are like $20
It's algae, you are using too much water. What I do is grab a bag of Pearlite and put a layer of that atop the soil, keeps that and bugs away.
Water twice a week in veg, thrice a week in flower.
Droopy leaves indicate over or underwatering, since yours were regular shaped and haven't gone wrinkly yet it looks like overwatering. You should be topping that pot off twice a week at tops while they're that small. In my opinion water twice a week in veg, 3 times a week in flower.
You're welcome. Super smart putting an open fan right above the plants, that's called a light-leak in fact but I'm sure that's excluded from your list of light leaks cause ... light's not fast enough to pass though a spinning fan?
That things shit, you can't put any weight in it and it's just a big light leak. It'll be half-covered in duct tape and reinforced with wood before it'll be useful.