Deficiency?

Hey Growmie, Doesn't look like a Magnesium deficiency but it does look like your plant is suffering from nutrient burn or too much nutrients. It always starts with the burnt tips and in this case with the last two photos having dark shiny green leaves it could be nitrogen toxicity meaning your plant has too much nitrogen in the soil. Another thing to check would be if the lights are too close it could be light stress. Hopefully, I answered your question and remember ..."Happy Growing" and "Free your mind one puff at a time".