Since you asked, foundational support consists of factual information, evidence, and reasoning that leads a person to their conclusion. If I don't supply it with every conclusion, you know I'm always ready to. More than 3/4 of what I wrote is in support of my positions and if anyone sincerely feels there is more support needed, one has only to ask.
Foundational: (Mg deficiency] presents in citrus first as chlorotic spots near the leaf stem, between the midrib and leaf margin. As the deficiency progresses, the entire leaf becomes chlorotic except for an arrowhead-shaped green spot at the base of the leaf with the tip of the arrowhead pointing at the leaf tip. It's difficult to tell just exactly what it is, but it appears likely to be a micronutrient deficiency (possibly manganese and/or zinc), or, potentially being caused by an EC/TDS level too high (too much salt in the soil [solution]).
In any case, and even if it was a Mg deficiency, the best way to remedy a deficiency is not by guessing at what nutrient might be deficient and acting on supplying that nutrient alone. The knee-jerk reaction would be to dose with Epsom salts for its Mg content, but that can present it's own issues, like masking the actual deficiency and limiting uptake of Ca(lcium) and potassium (K).
I spoke of the fact that Mg is a mobile nutrient and as such a deficiency would be more conspicuous in older foliage, and there is obviously no hint of that in Doc's image.
When this wasn't enough, I went looking and found/provided images, text, and and a link to a FSU Guide to Citrus Nutritional Deficiency and Toxicity Identification, which showed how a Mg deficiency presents in citrus. Virtually all I said upthread was supported with information based on plant physiology, soil science, and a line of reasoning people can follow.
In this thread and many others, and if one pays particular attention, a repetitive and intentional pattern becomes clear. Habitual incorrect use of my user name, nasty comments, and the anagram (TLTR, which = 'too long to read') posted after many of my longer offerings gives readers a glimpse of their author's mindset. Who can disagree with the idea the wasted energy might better have been put toward producing light, but was instead purposed to the creation of heat? I don't really mind these little jabs because I realize that in putting a lack of self control on display, one grants authority to the object of derision.
Al
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