hey i understand it is like something is happening to your kid

and when you see an issue it is ALREADY an issue for some time to the plant and takes longer for us to see it
if in general you think you might have a soil temp issue you can put reflecting things like even cheap aluminum foil to lessen the soil being light saturated other than increasing the distance of the light
yes this will lessen the severity of a problem because you are lessining the amount of imbalance incoming energy from light to the plant so it will reduce the dramatic effect of a closer light giving more energy to exaserbate an already occuring problem(giving it a rest) so to speak but it is really giving you a rest to fix what the plant is telling you

cal/mag or nitrogen and iron could be the issue but at this stage in the game if there are any cal/mag ie. other issues i would tend to lean towards ph
and if you say ph is ok then i say well is it reading ok but actually off inside the medium
cal/mag at earlier stages really would stage from other issues other than underfeeding
truthfully if this was the case mag usually shows to the eye first
the real question is why the issue to begin w/????????