Magnesium deficiency?

forgot the typical caveat -- local water may contribute some plant-available nutes, so that can cause minor deviations to the ppms from fertilizer that you need. No matter what, trial and error is necessary to hone it to your local climate. Your local common VPD will impact overall concentration needed, but once you find a good set of ratios that grows 99% of all plants exceedingly well, it's more a matter of overall concentration matching local variables that impact rate at which a plant drinks.

Your plant isn't old enough to show an Mg deficiency. It's not people on this site.. it's existing knowledge you can look up if so inclined. I have hard water.. 75-80ppm Mg is what i need, give or take a bit. My water may be adding some. So, you still need to rely on observing and reacting. When i adjust Mg, i make a note on my calender 5 weeks out to start paying attention for any symptoms. Calculated from labels not some inaccurate TDS pen: N 120-130 P 40-60 K 180-200 Ca 100+ Mg 75ish S 100-110 this will vary in overall concentration, but the ratios are very solid. Again, not "my" ratios but evidence based knowledge used my multiple fertilizer manufacturers (jacks, southern ag, masterblend, even Athena's dry pro line, if you want to spend 5x more than you need to for the same exact shit, lol) It's no accident or coincidence their "pro" lines or hydro lines all have a very similar ratio of nutes once mixed. pH around 6 is fine. a couple tenths either way will not be a difference your eyes can resolve nor a handful of plants with greater resolution than eyes. 430ppfd? so you measured in multiple locations across entire canopy and averaged it out? PPFD is about PAR/s per meter-squared. It's not a single-point measurement. that would be PPF or PPE. Also, if using a phone app that value is +/- 10-15% because all it is doing is converting a klux measurement. A phone is not a quantum meter. Not capable of measuring PPF/PPE. Easy to rule out light -- are the new nodes stackign on top of each other with no internode development/length? if so, light is a suspect. If feeding at .7EC, it's probably just in need of more fertilizer. Depending on ratios given, it may not be all of them, but likely at least some at ~400ppm. (EC is better, i used ppm her to relate to the ppm calcualted above from guaranteed labels. PPM from a TDS pen, no matter the cost, is a conversion from electrical conductivity and is not accurate.. it's maybe accurate, lol... you can see this by the fact that each manufacturer may use a drastically different conversion factor from EC.simply google EC conversion factors - 500-, 700- 1000-scale, think there is a fourth too)

Ask yourself what are you feeding them? and then look to see if that has any magnesium in it. I you can't tell email the brand of the fertilizer and ask them. If no, then likely Mg, Mg has a wide availability from the substrate PH and if its in a ready to take in form like epsom salts then their is no issue with it taking it in. Most liquid nutrients for cannabis are all the same compounds suspended in liquid form all available for plants to uptake.

Check runoff first. Your coco pH might be creaping up a little. IMO it's better to run a little acidic in veg, like 5.8