Thin seedlings

[Reinheitsgebot]

I was unable to find a similar post so please forgive me if this has been covered at some point.

Every year seems like a different problem for me when it comes to starting tomato seeds. I never seems to have issues with peppers, but I digress. Does anyone have any insight as to what might be causing the issue pictured and whether it can be remedied? I started my seeds in a flat on a heat mat with a proper soil mix from a local greenhouse. I covered it with plastic wrap that was flipped daily until most of the seeds had germinated. I then discarded the plastic covering and moved them under the grow lights, where they have been for about a week now. In all the pictures I have seen from people who have a handle on this, their seedlings look thicker and vertical as opposed to the horizontal growth I am seeing. Is there a fix? Is it too late to start over for a zone 5 garden?