AsNoriuanswered grow question 4 years ago No its not normal !!!!. There should be reply option to given answer.
Pistils goes brown with maturity at week 4-5 of flower.
Earlier it could be influenced by actual touching/bruising , check how fan moves leaves, maybe some buds are touched and that makes them brown.
Hi temps lead to getting brown earlier, don't go higher than 30
cel.
Late watering could be the reason too.
Ph inbalance, nute overdose/toxicity/lockout can be the issue.
Water on bud, some people spray flowers - that leads to getting them brown too.
Check them and keep girl happy. Pistils won't be white again, but it shouldn't influence your harvest a lot, but if you won't sort problem which makes them brown - that could lead to poor harvest.
Good luck !