HELP on my BLACKWATER SEEDLING

So I had a real nice darkgreen vibrant seedling ,then it turned yellow with turned under leaves with the 2nd stage of leaves.I thought that is was water logged so I transplanted it in fresh organic choice soil[the same I used to start all my beans. I added some worm castings to the mix and put in the sickly little blackwater plants.in the newer soil and wet it up a bit. Shrinking and yellowed, so has the symptoms of lacking nitrogen .2 weeks later and they still look helpless.and without any growth whatsoever, and they were reference looking in the first 2 weeks. and then the downward spiral. today I gave her a weak mix spray of Neptune fish emulsion.but my confidence is not up to par.. a couple other different strains appear to have the same symptoms. but others don't same water.same everything,,so I am at wits end, can anybody shed some light on what the heck is happening ?

Any pics by any chance?

The soil you are using is way too hot fro this strain, go for a very mild seedling mix, then after 2-3 weeks of growth potup to a mix of FFOF and 40% perlite.

this is a very upmarket strain that requires upmarket care

Ok. What a schmuck I am., I looked more carefully at the healthy plants that are very close to my sick ones..
GOT MITES. So they probably were the culprits that sucked the juice out of my small seedlings