Hello! Led distance seems alright.
I think you have some thrips infestation on some of your plants, look out for stains showing up on the surface of the leaves, with a slight silvery sheen and some leaves appears brittle by the loss of chlorophyll and are dry, check pic 7/8 on the last plant is more obvious.
It is difficult to spot them at first, but the damage they do is typical.
I would fumigate room and spray plants with neem and leave the topsoil dry well in between watering and removing leaves who are too damaged as thrips lay their eggs inside leaves.
Act quickly and plants will perk up... I had same problem and plants looked the same, they came back to full health! Good luck
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