I'm no expert, but if you've got increased nitrites, you probably have a lower nitrate level. Yes??? I'd be inclined to think it could be a lack of nitrate (and subsequent N uptake necessary for leaf growth) rather than nitrite damage. Once the cycle finds its balance again, it could show signs of improvemant.
I don't know the intricacies of the process, but I understand that in the absence of nitrAtes, plants will use nitrItes as well as raw ammonia for their nitrogen needs.