spots on pony tail palm

Nolina recurvata? Closest picture I can find.
10 year old.
Full screaming hot morning and afternoon sun indoor houseplant (atrium at a College) Yellow spots on old growth, no pots on new growth. Yellow spots are block shaped like the parallel veination. Spots range in size from 1/8 inch to 1/4 inch.
No thrips, mites, mealy or scale. Minimal fert. in spring. Dishsoap, alcohol and lemonjuice to wash leaves occasionally.
Whats its problem? Any ideas?
Thanks for your advice
Susiecatt
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Beaucarnea recurvata is the plant's correct name but many horticultural refernces place it in Nolina in ignorance of the botanical difference between the two genera.
No true Nolina species form a caudex (even the caulescent species) and the fruit structure is very different.

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Ah yes... thanks Cereoid
Beaucarnea recurvata is the plant's correct name but many horticultural refernces place it in Nolina in ignorance of the botanical difference between the two genera.
No true Nolina species form a caudex (even the caulescent species) and the fruit structure is very different.

Yellow > spots are block shaped like the parallel veination. Spots range in size > from 1/8 inch to 1/4 inch.

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