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Looks like localized nitro + magnesium (to a lesser extent) deficiency.
And yes the lighting also affects that (coz chlorophyll is only useful with light).
Other leaves are looking perfectly healthy.. it's only at the bottom so I'd be leaning more to them not getting any light. If it starts to spread then yeah its N. But your other leaves look nice and dark mate. I'd just keep an eye on her 👍