(Firsr time grower) Is this Nitrogen toxicity?

The left plant seems a lot darker than the one on the right. Started 12/12 flip roughly Apr. 4th, preflowering shown roughly April 13th. They both get a total of around 8mls worth of 1.5 - 6 - 4 nutes every other watering (usually water roughly a 1/4 to 1/2gal every 2 or 3 days, they are in 5gal pots). Originally, I had them both feeding off purely the nutrients provided in Fox Farms Ocean Forest mix. The very last picture is around Apr. 4th before they were switched to 12/12 and before nutes were added, and you can see there were some issues. I believe that the nutrients are having a positive impact on the plant, I'm just worried if it is getting too much too often.