The browning tips may be lack of something, but give them straight water on their next watering. Over-all, I think they look very good and the majority of the brown leaves are from change in light and temps. As long as mine are losing leaves from the lower extremities, I do not concerned. Top leaves, then I like to monitor more closely. I find that they can shed their leaves and within a few weeks to a month they start producing more.
If they are in a soil-less mix and do not have added slow release fertilizer to mix. If in leaf, I fertilize mine every time with a 1/4 strength every time I water. Occasionally flush with plain water. Watering dependent on what the trees need for the time of year and growth cycle.
I am sure I do not need to tell you about fertilizer/fertilizing. As KD mentions. A fertilizer w the elements that she states are definitely important for good growth and vigor.
Rick
