You list the weight of your water but you don't mention the pH? And you don't have a PPM meter which you need; I'd recommend you get a pH and PPM meter asap & go from there
www.thcfarmer.com
You're chasing shadows Eclipse (get the pun?) Suggested above ^ what is causing your issue; stop by 'the beach house' in grow journals if you have any specific questions or would like some recommendations, good luck!
Edit: please don't try blowing your tent up like a balloon
you should always have negative pressure, and in my opinion you should never shut your inline fan off; the exception might be if it's on a humidity controller
To each his own Beachwalker! If it works for you then go for it, but like said in my comments i run CO2 you NEVER use negative air pressure when running CO2! Plus there are pros and cons to both methods! But for the record positive air has far greater pros then cons
Reasons Positive air pressure is better:
1) Balancing Humidity, Temps, and Air flow- because when you exhaust air out you are displacing the air outside of your room which you lose the benefit of controlled ambient air because all the ambient air is outside ur tent/ room now.
2) If you put a HEPA filter to the intake fan then no external Bacteria/ Mold cannot adequately thrive (look up how they setup sterile science labs if you dont believe the statement)
3) It cycles the Co2 if being used because the co2 that gets pushed out of the tent getting blown back into the tent, but in negative pressure you lose your CO2 the moment you exhaust air outside your room any CO2 that builds up is now gone it will not come back into the room faster then you are sucking it out.
4) when you create a negative air pressure you are basically making a vacuumed space... And in any vacuumed space you have lack of oxygen because the oxygen is getting displaced faster then it can come back into the room, since your roots thrive on oxygen this concept is counterproductive as well as any beneficial microorganisms thrive in aerobic (oxygen rich) environments, thus making negative air pressure rooms a breeding ground for anaerobic bacteria and fungi!
The only con to positive air pressure is that you cant vent the smell like you do when you exhaust... But thats why all the big time growers do recirculating carbon air filter.
Seeing as these are scientific facts and have been tested, tried and are true i will wait for your reply on source material that contradicts my info!
Look forward to your reply Beachwalker!