Why My Magnolias Are Losing Alot Of Leaves

Question

I have a number of little gems that are planted behind a retaining wall, they are about 4 to 5 years old and are now about 2.5 meters tall, about 5 months ago they started to lose alot of their foliage, we have a drip watering system that is working. They seem to come good and then it starts again I have attached photos

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Answer 1

Some varieties of magnolia drop their trees seasonally. Yours may be deciduous. Here's an article about that:
https://www.gardeningknowhow.com/ornamental/trees/magnolia/which-magnolias-are-deciduous.htm
If they're turning yellow and dropping, this article may help:
https://www.gardeningknowhow.com/ornamental/trees/magnolia/yellow-magnolia-leaves.htm