Answer: Star jasmine is not susceptible to any particular diseases so I'd look at the soil drainage (or lack of) for clues. Your plants need to be watered regularly but if the soil remains soggy for lengths of time, the roots can rot and the tops of the plants will die. Try watering as usual and then waiting 3-4 days. Dig a hole near the roots of your plant; if the soil is moist 3" beneath the surface, it drains well enough; if it's dry, you didn't apply enough water; if it's soggy wet, the site doesn't drain fast enough. The leaves of star jasmine can turn red if the weather gets cold or if there's a lace of potassium or phosphorus in the soil. As for the tree roots - if the tree is dead, the roots won't be sucking water or nutrients from the soil, but they may be decomposing, which could use up the nitrogen in the soil. Pine needles are acidic and if the soil pH has changed, that might account for the inability of the jasmine's roots to take up the nutrients it needs. I'd check the soil pH and the moisture as above, and feed lightly with a 10-10-10 general purpose fertilizer. (Apply in amounts as recommended on the package.)
Best wishes with your star jasmine!
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