The problem with certain hydrohuts is that they are apparently made with some sort of vinyl or problem IN the vinyl that apparently causes some sort of gas or emission that THEN causees suffocation in cannabis plants. That link is to an announcement by the Hydrohut people admitting the issue and offering to fix any defective Hydrohat. Included in the announcement is an e-mail address so he can contact the Hydrohut people and have his fixed.

If you read the thread very carefully he pretty much says that everything that went into the hut turned yellow.....and whenever something came out of the hut it improved.
Classic symptoms old chap!