The Pineapple chunk smokers digest

Things have taken a bit of a turn for the worse this week, the dominant plant has developed some sort of problem. Leaves are turning yellow, and mottling. I’ve looked through grow questions and came up with a magnesium deficiency, but wasn’t sure. So i flushed both the plants, and then today added calmag, biopsys and flourish back in. Really hoping to see an improvement in her, the plant on the left has now almost caught up and the buds are flattering up, the plant on the right has barely moved this week, just looking less healthy. It’s weird as both plants have always been treated the same, I can only hope the dominant plant just used up all the resources in the soil and is begging for a feed. Any advice is appreciated. On a happier note, the plant on the left is really fattening up nicely.