After watering and fertilizing the flax with kelp meal and letting it do its thing for a couple days, I went back to the farm to check on it and see how its doing:
It’s pretty clear that the plants are doing a lot better after only two days. The yellowing has reduced quite a bit, they are standing much straighter, and some have even begun to darken to a much richer green color. This leads me to believe that fertilizing the bed was the right move. Since it’s hard to say whether or not water also played a role in the yellowing (plants use water to absorb nutrients so either way it could have been partially responsible), so, I am planning to continue applying foliar spray weekly as well as watering a bit more frequently until the plants are well established.