I know how you feel, I was actually having panic attacks over my tent, really, serious panic attacks. Time was ticking away and I could not resolve my problems nohow.
Here is what I did to finally prove the point of my tent offgassing. Take one out, and get it under a light outside the tent, preferably in another room dont worry too much about fans or reflective surfaces for a minute and obviously handwater. If it starts to recover after a few days it is the tent. I took them out, they recovered, put them back in, they suffered after a few days. back out ok, back in suffered, I was that stubborn it took a month of doing this after trying everything else (throughout about 3months prior,different nutes, tanks, tank changes, different clones,high humidity, low humidity, different lamps, different water, everything!),Then I googled grow tent problems as an absolute last resort and found the link i posted. next day i took them out of the faulty tent and put them in my old one, it has been 2.5 weeks now and the plants that i thought i couldnt save (they were really, really bad, way worse than yours), have easily quadrupled in size and are really, really taking off now, started 12/12 yesterday. The reason I question the tent is that you havent had a successful grow in it yet have you? Growing good weed isn't that hard really, its not. most problems for new growers is overwatering or overfeeding, and with ionic i never, ever had a problem with nutes and we are experimenting with the watering, so i'm pretty sure it is an envornmental problem. If you got it on ebay or searched for the cheapest tent you could get it is almost certainly made of pvc. Hopefully, problem solved. The smell you mention says poison gasses to me. You dont seem to be getting any roots down which is almost more important than whats going on up top (no roots no shoots!) my problem exactly. plants dying from the bottom up? yep

If the plant outside the tent recovers (and it wont take long), take the covers off and get them out of your house, especially if you have pets or children, then get some white/black plastic from the hydroshop and cover the frame in it to make a temporary cover. dont buy pvc plastic obviously, make sure it is from a growshop! (until you can afford a homebox or 2) you should be able to get some stick on zippers off the net too. Don't forget to remove the drip tray as this will be made of the same nasty stuff!

Those leaves on the bottom look suspiciously familiar.

Keep me in the loop,
Subzero :jointsmile: