I assume circumstances require cutting today? If not, let them go another four days, they'll only get better. If I had to cut and not hang for four days I would trim the buds while green and the leaves were still firm. Makes for easy trimming. Remove the buds from the stems and spread one layer...
HPS works fine for a whole grow. Keep the light as close as possible without burning them. Hold your hand at plant height, if it's too hot for our hand it's too close.
Clip off the main growing tip and the plant will be shorter and bushier.
If you have mites they'll be on the underside of the leaf, small but easy to see with magnification. They look like little light brown crabs.
You probably have a house spider. Lower leaves often turn brown close to harvest.
First of all.....there's nothing wrong with 81.5, plants will grow fine.
Fans probably cause a wind chill. The leaves respire O2 and H2O, the breeze from the fan will have an evaporative cooling effect.
Not safe, it will pollinate all of your plants. Looks like a nice strain. If possible you should move it to a location far from your girls and let it seed. It will still smoke pretty good and you'll have seeds.