Could be.. The white plastic lined tents became toxic a few years ago when the cat who manufactured them for like 10 companies started using a material that off-gassed.
I'd return it if you can and get a silver lined tent of some kind. If not, start rounds of test seeds. Here's what will happen to them within weeks if your tent is affected:
Early symptoms:
Late:
Thread about the issue here:
http://www.icmag.com/ic/showthread.php?t=103953