Sounds like some of the stems get more light exposure than others and got a little bit of a "tan". Just from what you say and the pictures of a healthy looking plant you've posted.
I took some pics of the red stem so you can see it
So are you saying I do have cal mag deficiencies
They're totally fine. Carry on.
I'm growing in hydro I've been feeding 3 part advanced nutrients and cal mag and Kool bloom 3 tsp of bloom per gallon 1 tsp of grow per gallon 1 tsp of micro per gallon 1 tsp of cal mag per gallon 1 tsp of Kool bloom per gallon but I'm out of my bloom nutes so today I'm going to start running sensi bloom part a and b at 3 tsp per gallon 1 tsp of Kool bloom per gallon and 2 tsp of cal mag per gallon
Pictures without the grow light on would be best. Grow lights off camera flash on. They look light green but could just be the grow lights.
Pics without grow light plants are 27 days since I switched to 12/12 in these pics
Leaves look normal color but the serrated edges are curling. Usually cause from light or heat stress. I'd check your light distance/intensity and temperatures.
They're fine but like said above there's probably something you could tune in but there's nothing I'm seeing that says the plants are in any real distress.
