Leaves yellowing

Hi everyone,
It's the 10th day as I put my small germinated plants to there new growing "coco coir" growing medium I did some mistakes in the begining due to my first time growing and I watered the plants the first day with fertiliser 0,5 EC 5.7pH some of them died because of root burn but the others recovered. Two days ago as they are big enough (I think) I watered them with fertiliser again 0.6EC 5.8pH and some of the leaves I see are a little yellow and I don't see signs of grow in two of my plants the other two are okay. Can somebody give me an advise what should I do. Should I water I still water them with plain water again or should I keep feeding them with fertiliser.
Thank you and best regards.

The pictures are the difference between the two plants who one of them feed very well and grow the orhers leavs are a little yellow and there is no signs of grow for two days

Provide more detailed pictures please

My phone does not take so good pictures but maybe you can see a little yellow underneath under the lamp I can see it better and there is no signs of grow since I watered it the last time the others are doing way too better

All I can say now is leave it dry out rough, than water with pHed to 6,5 and watch the runoff. Than you will know more. At first sight I would guess overwatering...

Keep your EC low, so you don't burn the plants...but for sure, every time you water, make sure you're feeding the plant. Do not give them plain water. Keep your pH where you've been @5.8 Good luck.

She is probably working on roots now, so make you sure that the temperature in the root zone is pleasant 22-24 degrees of Celsius. Because of mediums out drying temperature likes to fall down to 15,9 when your room temperature is 20 and this is too low for the roots, you should keep it at least 18.