HYDRO First DWC Hydro grow. Not growing and a little yellowing of "old" leaves

[MithrilSCYTHE]

First DWC hydro grow, this is a seedling\youngling of a Royal AK. She keeps sprouting new leaves but she doesn't gain internodal space and so, she stay flat.
yesterday I noted the first sign of yellowing.
Is this magnesium deficiency?
I've looked up at the pH availability of nutrients and I suspect that, since I've always kept my pH below 5.9 amd I've seen that magnesium can't be absorbed much below 5.8
I need a confirmation before taking action.
Also, beside raising my pH a bit, should I use epsom salts via foliar spray? I already have a teaspoon of them in the solution (1,5 gallons)

[Campesino]

Yeah, could be Ca too.
Curious about what kind of water you are starting with and if you have been giving adequate Ca and Mg in nutrients thus far. But it could be from consistently low pH... good reason to let it drift around.
What nutes are you using and what PPM/EC are you running?

[Campesino]

Sorry, not low - not sure what I was thinking - that is on target

[MithrilSCYTHE]

Thank you! Also, since no one was answering I went along, and I've proceeded to snip of some of the leaves since it was all so dense that it started to bend under its own weight and space.
I selected the worst leaves. Did I messed up or is it ok?
I'm not caring at all how much will it take to re establish and reaching the end of the plant life, I'm not in a hurry, so I don't care if it will slow down, I just don't want her to die

[Campesino]

Didn't mess up! They weren't likely to recover. I think she'll do better now if you let pH drift a bit.
Cheers!