Answer: Liquidambar (sweetgum) has no serious insect or disease problems so I suspect the leaf problems are cultural in nature. Premature yellowing of leaves with brown tips indicates a water stress. Too much water (in poorly draining soils) can deplete the oxygen that roots need to survive; not enough water (droughty conditions) can cause yellowing and dropping leaves. Too much fertilizer can burn the roots, causing browning tips.
Hope this gives you some insight into what might be happening to the tree.
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