With new nutrent solution I'm at 760ppm ph 5.0. Using MaxiGro from GH. Tried to stay organic with Pure Blend. In the 1st few weeks I had the ppm around 500 and increased the ppm just to try to boost growth. Will see if new food will make them grow.couldnt agree more.
your ppms are too high for a seedling of that age.
7-850ppm might be a better ballpark to back up into....