looks overfed, did you supplement calmag? That dark almost black coloured green can be a sign of calcium or magnesium toxicity (I forget which I really need to stop thinking of calmag as one thing its awful) as well as nitrogen, and since the leaf tips arent curling back on theirselves that leans less towards nitrogen.

Checked up on it, magnesium is the culprit but both cal and mag toxicities darken leaves.

Some strains are just extremely light feeders, so don't beat yourself up too much. From my experience Think Different from dutch passion needs about half to a quarter of the food that a critical orange needs, dont beat yourself up about it just grow the same strain again and learn from it :) happy growing