I usually veg an initial grouping of plants and then take 2-3 clones off each of them then I flower plants I've taken clones from and will either keep or cull the clones I took as mothers depending on the results of flower. It's a.long process but it stops you from wasting whole grows on bad...
They need more space than most tents can provide anyway. 30-36 above canopy and 15inches back clearance. That's leaving 3 feet for pots and plants in most 6 anda half feet tents which is doable but not really ideal.
The height you have the light at in the pictures looks pretty good. I wouldn't put it too much closer ot you're gonna get some more burning like you have on one or two of those plants.
Yes. Most feeding schedules that companies give are far too heavy. Next water or two give them just plain water so the plant can use up the excess salts.
I wouldnt run less than 500 watts actual draw Led in a 4x4 depending on the efficiency of the lights. Most 500-650 watt actual draw fixtures are sized for a 4x4 footprint.
Also those burnt tips on the rest of your leaves are indicative of over fertilization. Nutrient burn. Youre probably just about to hit nute lockout. Dial your fertilization strength back