Something strange is happened with one of my collard green plants. It is planted right beside the others and treated in the exact same way (No, not the tiny one,something is wrong with that one too. the one in the bottom left corner is the concern)The others are growing perfectly, but this was showing troubling symptoms on it's new leaves. When they were first growing, the spots between the veins looked yellow and wilted. As the leaves grew in size, that gave way to dead brown patches and holes eventually forming. The new leaves on this plant in the centre are also showing similar signs.

Any thoughts?

Need any background on my garden?
This is my first year with this garden. I caved in and filled an inground pool with "clean fill" then set up 8 raised beds, 1 foot tall, over the space. The beds were filed with topsoil and ammended with alfalfa pellets, rotted leaves, bagged manure and worm compost tea. My soil isn't great, it's pretty sandy, but has been dug and mixed thoroughly.

Thanks, Kurt