Because Mag is the most needed nute in a good garden, its the first thing that gets depleted if there isnt enough of it because it is the main function for photosynthesis. And when people drive the LEDs so hard on the plants, the MAG uptake is accelerated, NOT CAL, just mag, and then potassium, this is why many peoples plants go to shit in week 2-3 of flower.
I still say, its over watered, because its being treated like HYDRO, and the roots are rotting because Mag isnt being uptaken because of the constant dampness of the root ball.
that plant is in a 30 gallon pot, it shouldnt needed watered for 2 dang weeks AT LEAST.
HYDRO, is when you pour water, and the container doesnt hold any, OR your roots LIVE IN JUST WATER AND NUTES,