That's not a blight. I've got a whole plant with leaves like that right now. It was a combination of things. Such as:
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1) Root pests. Check around the bottom of the main stem for root aphids or scale. If you've got ants building a dirt trail up the main stem, time to take action.
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2) It's been raining. A lot. That's washing out nutrients. I would really consider getting a top dressing of vermicompost, along with a dry organic, and a bit of kelp meal, down on top of the containers. Not much. Maybe a 1/4" layer, or so. Or, if you prefer "fertilizer", put down as good of an OsmoCote type fert as you're willing to spend $ on. As much as I hate recommending that, they can be very useful here in the land of monsoons.
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3) Seasonal adjustment. I have a lot of multi-year plants, and when the weather changes over from cooler to regular Florida, they go through this, frequently.
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4) Media issues. I have a strain of some sort of mycelium that always grows like cancer in my beds, and produces little orange mushrooms. It's great later on in the season, but at first, it makes the raised bed mixes sort like dry bread. I haven't figured out the dynamic yet, but it all works out later.
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One more thing to be aware of... This might also be roots getting overheated. Make sure that you aren't in small black containers, in direct sun for 12+ hours a day. They'll cook. And it does look kinda like that. Sometimes, one issue will mimic another. You have to be careful. If it's constantly raining, that disrupts nutrient uptake, and it can look like you have a deficiency. Even though, there may be nutes a' plenty. (they are just not able to get in) Overheated roots can look like nutrient deficiency OR a lack of water. Too much water can look like not enough. Etc, etc, etc.
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I concur that more pics would be good. As much info as possible. Age of plants, size, hardening off process, location of planting, what they're planted in, etc, etc, etc.