Leafs

Yellow appears when the PH is too high or when there is Magnesion deiciency. Id sugges to ad some MG & Cal supplement or to water with a 5.7 PH water. Brown is over watering so you’d have to find the balance there but these things always happen even to the best through Veg. Once you are in flowring they will eat alot and also the Flower fase nutrients have will balance these initial deficiencies.

I would make sure that your girl doesn't have nutrient burn by testing the runoff whenever you can. Not sure the exact ppm off the top of my head that you would want to be in at that stage if u have a TDS tester as well as ph levels if they tend to be fluctuating. Otherwise, if the problem doesn't occur in the newer leaves or the same level leaves, I wouldn't worry too much. Just steps that I would take from what I know of what I've learned so far ;)