Answer: Browning can be caused by a number of different factors ranging from over or underwatering to pest or disease. While underwatering could certainly cause brown tips due to water stress, this particular plant is sensitive to overwatering and will suffer root problems in overly moist soil.
Although it seems like watering every day would be the right thing to do, unfortunately this is not the case.
Your goal in watering would be to supplement natural rainfall to keep the soil evenly moist but not sopping wet. You need to dig down with your finger and see if and when you need to water. Watering is best done deeply and less often rather than daily. It is a good idea to water deeply, wait a few hours, and then dig down and see hoe effective your watering really was, sometimes it is surprising. Deep watering encourages deeper rooted plants and this is good because the roots will be down where the soil naturally stays moister longer. Using several inches of mulch over the root area (but not touching the trunk) also helps to keep the soil moister longer as well as keeps down weeds.
If your watering has been overhead watering or sprinkling, there is an increased possibility of a disease problem having developed. For this reason especially you might want to take a sample as well as possibly a photo of the overall plant to your local nursery professional and/or county extension for a more specific on-site diagnosis of the browning. I'm sorry I can't tell you with certainty what exactly is causing the problem.
I hope this helps you trouble shoot and I hope it is nothing serious.
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