I believe it’s heat related. Does sun shine directly on the container in which it grows? How much direct sun does the hardscape behind and under it receive? Those surfaces are passive solar collectors which reflect and radiate heat far longer than the period the sun shines directly on them. Sun shining directly on the pot sides physically cooks the roots, heating the soil inside and cooking out the soil moisture. The use of inorganic fertilizers in containers in hot periods can easily exacerbate the issue by causing them to break down faster in the irrigation water, over dosing the soil ball with too much “salt”. I don’t know what your watering schedule nor ferilizing routine are, but I would move the pot so there is at least three feet between the pot and plant and any walls the sun shines directly on to reduce some of the potential heat reflection/radiation. I’d also watch the water to insure the soil remains moist and the drainage allows the water and any dissolved salts from the water, fertilizers and soil to flush out instead of building up in a saucer or slow drainage. Think of a pot of soup simmering away on the stove for hours. As the water is boiled down, the saltiness of the remaining liquid increases dramatically. It’s particularly damaging to house plants where the irrigation water is allowed to drain into a saucer to evaporate, leaving the “salts” behind.The “damage” in your photo appears cultural and due to conditions instead of any “disease” issue. Container growing in heat can be a real “joy”. I did it in the Santa Clarita and San Fernando Valleys for over 50 years and am now doing it in northern Santa Barbara County. Even here were we have nowhere near the heat Southern California experiences, containers can be problems when the sun shines directly on them and the ever-present winds desiccate them very quickly. Good luck!
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