That surely is totally weird. Your veggies should have taken off like gangbusters.
I am not familiar with Leafgrow mix so Googled it. Claims to be organic. I dod find this link explaining Herbicide contaminated Compost.
https://extension.umd.edu/lear...
Sure does sound like this might have been your problem.
I would say add as much clean organic matter as you possibly can. Shredded fall leaves tilled into the soil would be a free alternative.
I avoid lawn clippings unless they are from my own lawn.
