Can someone plzz help with what is going on?

This could be a few things. Purple petioles can be a sign of deficiency . Phosphorus and calcium both will affect coloration of petioles, Lack of P will also cause very dark older leaves, with yellowing and necrotic patches, we know that in flower the plant starts hogging down Phosphorus, some plants way more than others. PPM in my opinion doesn't tell you much, you can have "perfect" ppm but still have problems if the N P K balance isn't right for that particular plant. You could try boosting phosphorus for one plant and see if the problems stops progressing. Your ph is fine for soil (6.5-6.8). let me know what you end up trying (message me). Happy growing.