What nutrient issue or disease starts with brown spots on leaf veins?

I first noticed an issue with this plant when these brown spots started showing up on the veins.
I ran through the usual checklist and couldn't figure out the issue.
Posted on another forum and didn't get an answer.
I ended up harvesting this plant prematurely but I would still like to nail down the issue in case it pops up in the future.
Without out any background information, what do you think this is?

Likely a calcium issue.

Renfro said:

Likely a calcium issue.

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I thought calcium issues started with interveinal spots.
Do they also start on the veins?

nunyabidness420 said:

I thought calcium issues started with interveinal spots.
Do they also start on the veins?

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I have seen it show up anywhere on a leaf and I have seen it be black dots and white dots.

Renfro said:

I have seen it show up anywhere on a leaf and I have seen it be black dots and white dots.

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Thank you!
The interveinal thing was throwing me off.

Renfro said:

Likely a calcium issue.

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Would Epsom salts fix it

jungle666 said:

Would Epsom salts fix it

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Epsom salt is magnesium so I doubt it will fix a calcium issue, but I've read those two are interlinked so
I had EDTA-Ca at the time so a foliar spray would have been my choice of treatment.

nunyabidness420 said:

Epsom salt is magnesium so I doubt it will fix a calcium issue, but I've read those two are interlinked so
I had EDTA-Ca at the time so a foliar spray would have been my choice of treatment.

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What type of folier spray

jungle666 said:

What type of folier spray

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This and water. Maybe some kind of agricultural surfactant if I could get my hands on some.