It happens with mostly cheaper tents that are too good to be true on the price tag.
The problem is called "off gassing"
There are toxic fumes that are spread through the tent. Nothing will grow in them.
The same thing could happen with buildings (no explanation of why nothing will grow) You could have toxins in the water (so i suggest trying RO, if you haven't)
Is there another building near you that manufacturers anything?
The CMH,
panda film, reflection....They are NOT the problem.
Do you know the ppms of CO2 in the room? I've been through, or seen every issue (or just about). There should be absolutely no reason your plants are not growing.
Are there any pro's on this forum? I mean guys who have been doing this 30+ years?
If you know of any, other than me, ask them, and you'll get the same answer.
Or Google Off gassing and cannabis.
I'm not 100%, but it's the best explanation i can think of, besides bunk seeds