I have a 4x4 tent with 2 400 hps for bloom with a 460cfm venting to attic the problem is every time I go to 12/12 the new growth turns yellow and eventually dies off, only happens on new growth I use r/o water 6.5ph and gro micro bloom from advanced please any ideas would be greatly appreciated

What are the temps in the tent during veg,verus flower?


Mr.O

temp at veg 76-86 temp at blm 70-84

what tent are you using there was some problems with older tents and certain makes and this was exactly what was happening when the tent heated up from the lights, they was letting of a toxic gas from the pvu, pvc used in the lining of the tents, they was making the plants go yellow then death follows .
If you do a search about it on google im sure you will find plenty of information of other people who have had exactly the same problems, im not saying that this is what is happening but it does sound a lot like it to me, is your tent white on the inside by any chance and what make is it, and i will try to check it out for you.

You want lower temps in Veg-- higher in bloom-- then lower again at the end of bloom -- to mimic outdoor seasons...

The yellowing of new growth could be a nute issue-- do you flush when you switch to 12/12 before changing to bloom nutes?

What exactly do you use for ferts, and on what type of feeding schedule---
blooming plants have different needs than vegging plants....

and check the temps during lights out.... if it is a drastic drop--- that could be your problem... During lights on-- over 78-80f is too much....

How close are the lights? If you can feel the heat on the back of your hand at the top of the plant-- it is too close... 1 400w HPS is plenty for a 4x4 space... yes- more light is good-- but the heat issue in a small enclosed area is more of an issue.

Remember too-- if using RO water- you MUST add micro-nutrients as you have removed all minerals from the water!! Super-Cal Mag or Earth Juice Micro-Blast work well.


And check on-line for grow-tent recalls!!! Some were taken off the market because they give off chemical vapors at temps over 70f!!

Good Luck!

Yes I do fear the tent may be my issue it is white on the inside and is older i cant find a brand name on it and of course I got it second hand I am going to do a test in a closet and see if maybe this is it I had no idea the toxic fumes were apparent at 70 deg i thought it would have to be way over 100 to give off any fumes... i cant find a brand name on it and of course I got it second hand.. thanks for all input and keep it coming that is the only thing I havent changed

post a picture of your hut. i had a hydrohut and a sunhut cause me 1 year of problems before i figured it out. the only hut with white lining that ive heard not cause any problems was the homebox ( i still have 1 ) , but post a pic so we can help you out