Cant tell you much because you didn't post pictures of your whole setup.
Get a laser point thermostat and point at the leaf and see what temps are.
You shouldn't worry about light, because the plant is so small it dosent even need much light,
My theory is that drying the weed is something like cooking.
Try to do it to fast and your gonna lose smell and taste.
Last thing I want is my crop to come out smelling like grass or hay.
I see alot of people do that method so I cant say anything. but if you have a dehumidifier should be fine...
Top one is Super Silver Haze (HTCC Winner 4 times i think lol)
The Middle is Plushberry TGA
The last is SUper silve haze popcorn nug with SSH hash and SSH drysift lol
The best dry is done with NOTHING taken off the plant. NO fan leaves Nothing. Cut at the stock and hang her up in a cold cold room. Should take 3-4 weeks to dry and will come out FIRE!
I beielve if you cut anything off before hand it will call for a uneven dry and it will probably need a jaring.
That plant is gonna continue to grow like a weed if you dont train it. Looks pretty green. That leaf died most likely from lack of light. Happens to me all the time. Need to open that plant up to make a canopy :)