Did you feed? Sounds like they got more nitrogen than anything else.
Before I even read "I suspect the goodness had gone into the leaves" I thought of an experement I did some years ago; vitamin B1 (yes, the same chemical humans use) is used by plants to grow roots. I used a small pinch off of one pill disolved in 1 gallon of water to feed some seedlings. They seemed to stop growing as soon as I did. I pulled a few up a month later and they had gigantic, well developed roots. just a few little leaves. I assume I gave them to much of the B1 and actually stunted the leaf growth. I suggest maybe you have the reverse problem; Try using a lot less nitrogen. Lawn food is all nitrogen; even if they are just near it that could be doing it.
You might also want to carry on my B1 work (it worked great on tulips and lilys) but be careful, a little goes a long way.
Also Mods, could you move this thread to "off topic"?