How's it look and a couple of questions.

NL 5 weeks from 12/12. 4 weeks from first sign of flower. Is this considered 4 weeks flowering? Some of the hairs or pistols, not many and mostly on the lower buds turned brown. Is that normal?

Looking good.
Its more normal for the them to mature faster on top, but not uncommon for lower bud sights to reach maturity before their high altitude counter parts.
I would start site harvesting the sh*t turning brown, as its past its optimal potency and you dont want it the THC to degrade any further whilst waiting for your main kola to mature. Rip some of that popcorn turning brown and get a sample of whats to come, looks like you've earned it.

it looks good redroot....