I live in Massachusetts.I looked on Google about the "white powdery substance" and found good info.It is some type of mold that will not kill her but will deplete her vitamins.They say not enough air,light,not enough heat, and spraying her leaves with water.It is also very bad if she gets cold at night like near a window.Brown tips can indicate letting her dry out too much in between waterings.I have had 6 tulsi's for one year now and it very important to have plenty of light.Not just one set of plant lights on top but also on the sides and also a humidifier helps alot.If she gets bugs,spider mites etc., you can cover her pot as to not let her dirt fall out and dip her in a solution of water and Dr.Bronner's soap,put enough until the water looks milky.Then be sure to rinse her well. She realy likes this.Also remember to pluck her tops,starting at the first four set of leaves.She will split and grow two branches there.You should continue doing this.This ensures that she does not grow tall and skinny but bushy.A nice natural insecticide is citronella or lavender oils.you can sprinkle a little around her dirt but be careful not to let it get on her leaves it will turn them brown.I am no expert but am only sharing what I know from experience.Hare Krsna!
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