There could be several reasons why your Tulsi leaves have turned brown. It could be due to a lack of water, too much sun exposure, or even pests or diseases. If you suspect that one of these is the cause, try to address the issue accordingly. For example, if you think your plant isn't getting enough water, make sure to water it more regularly. If you think it's getting too much sun, try moving it to a shadier spot. And if you suspect pests or disease, treat the plant accordingly. With a little trial and error, you should be able to figure out what's causing the problem and get your Tulsi plant back to health in no time!