One is hungrier than the other.
All strains have their own traits, some need more food.
Other chances are if it has been locked out from too much food, doubtful if your other looks alright.
Or pH values being off affecting your plants uptake.

Pro tip: always measure pH and PPM, both in and out.

For future reference: taking pictures under natural lighting will help growers help you. HPS dulls the natural colours of the plant making it hard to properly diagnose issues.

Ph levels are alright i really like advance nutes for that reason.
ec levels are great too by checking run off with my ec pen. they are all raised out of the wells and run off water.
i was more think why is the dark plant dark without burnt tips showing no sign of an OD of nitrogen.

i see alot of post about dark plants getting cooked by fertz but im starting to think she might through some colour, due to this darkness. im not sure haha

the lighter green one is granDad purple auto and i give them both a fairly large nute doseage, are autos faster growing ? which requires more food ?
also thanks for replying man :)