joe you said it could be genetic and not environment as its one out of six but they are similar points.. as different genetics like different environments...for just one example some plants are just not perfectly happy until around 50-60% RH in veg, other plants couldn't care less... because of genetics.
Don't lower humidity anymore if its 40% that's already too low, 60% RH is great for veg. 40% is low but acceptable though you don't want to go lower for veg.
temps are a bit on the high side... 80f is hot, you could get away with it, but if ur already seeing 80f then you might get even higher peak temps especially during summer..
light seems too close, they already seem to be stacking hard so you want a bit more stretch in the growth you should raise your light a few inches at the least!
are the lights t5s? either way they seem too close...
With the ones you are hand watering (coco?) make sure to let the medium fully dry out right to the bottom before you water, every time, goes without saying water plants individually not all at the same time for your convenience, unless they need water, otherwise you are falling victim to what every new grower will experience at some point, overwatering.../ not letting the plant dry out
last thing, there is going to be so many beginners/mis-info for whatever reason who try to help when they don't understand shit, strange really as it just makes it worse rather than helping, like already you have one guy who gave the opposite advice to what you needed, humans eyy...
Peace.