well i think you should worry about them,, personally
i think i see similar issues on most of the plants,, tho maybe not all
i am no giver of advice about nutrient deficiencies or excesses, so i wont,
nor coco,, never used it so i have no clue,, but i know watering is important
plants look good other than the yellowing,, which is not actually yellowing,, yellowing is the whole leaf yellowing as one,, yours is dif
karma sent to them friend
for sexing,, especially if it is a sativa,, sativas for me show sex at about six weeks,, but one must look real close and know what one is seeing,, one can tell well before pistols showing, but must look close
indicas a bit sooner