Ebb and flow problem...why are my plants turning yellow? (merged)

Can any one answer this...it seems pretty simple but cant seem to get anything in plant problems to match ...i keep having a problem when i switch from one growth stage to the next ...i had ak47 and burmese kush plants in 4x4x4 rock wool cubes which i watered daily by hand with a basic flora nova grow and hygrozyme nutriernt mix the plants flourished ..i did this for almost 7 weeks and was able to sex out the true males...i then took my remaining females and put those into a 4'x4' ebb and flow table and set them up to get the same nutrient mix flooded in 3 times a day ...mind you there were no roots coming out of the bottom of the cubes they had been air pruned from growing out... . i had the water level set to just touch the bottoms of the rock wool cubes which were in white pots on top of about 4 inches of hydroton rocks...the cubes always stayed wet it seemed ..and 4 days later i noticed the growth tips begin to turn pale yellow...my ph is spot on 5.9-6.2 and my ppm is about 900...the same strength that they were getting when i was watering by hand....are the rockwool cubes just drowning the roots by holding too much water causing them to uptake not enough nutrients because they cant breath ...i have turned off the nutrient pump and just have a few air stones in the resevoir so that hopefully the rock wool cubes can dry out some.:(

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Did you put them in the pots with hydroton from the start?

You went from once a day watering to 3 times a day?

Sounds like the hydroton is hydrating and when it starts to evaporate the rock wool takes the humidity.

If the water was touching the bottom of the cube 3 times a day then it'd remain alot more wet than it was when you were watering by hand once a day...

Hmmmm.... pH seems fine ..

Maybe some different input from other members will help you solve this problem.

best of luck,
Bob.

well I don't know much about hydro but your issue looks like it could be an iron deficiency except the stems still look pretty green on the yellow leaves.

In some pictures I saw what I thought to be beginning symptoms of a Calcium deficiency.

Perhaps it's a Ca/Mag issue. I do see some minor curling going on along with the yellow.

I know Ca/Mag have to work together. Perhaps you're deficient on these and it's mimicking an iron deficiency since there aren't too many since of Ca being missing.

The rock wool stayed pretty dry when i was watering them by hand and they were just in a tray ...and now the cubes that are in the pots with the grow rocks were wet all the time ...could that have caused this i have heard that rock wool in hydroponic applications has a tendency to drown root and never dry out enough....and again this is the exact same nutrient solution they were getting b4 i transferred them to the flood table and put them in the pots..and they were super healthy b4 that...

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I would say if your plants were doing fine a week ago then back track to that setup and slowly start making changes so you can see what happened.

They don't look droopy to indicate that they are drowning.

Still looks like a deficiency of some sort to me.

edit: again I'm not great at troubleshooting problems, but I never will be unless I try right? Hopefully some pro comes in here with an answer/explanation.

I have discontinued the use of the flood drain pump and when the cube dry out to where they need water i will go back to watering by hand like b4... ...

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Originally Posted by zoomatl

I have discontinued the use of the flood drain pump and when the cube dry out to where they need water i will go back to watering by hand like b4... ...

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I think that you'll find this will solve your problem. Rockwool can indeed be too wet and it's east to get to that point.

Once they dry out, put them back in your system and hand-water them only as frequently as they need it. This should allow the roots to grow into the hydroton while keeping your rockwool from becoming overly-wet.

When the roots have grown out of the cubes, try to set up your ebb and flow again. This time, keep the rockwool out of the nutrients and let only the roots flood.

The guy at my hydro store advised i have a pathogen or bug of some kind...i have scrapped everything and will change out everything that is expendable including the pump...all i will have left is the res and the flood tray ...all the fittings and hoses will be replaced too...any other suggestions of how to clean and sterilize so the problem doesn't come back ...?..it actually looked like it had started clearing up but ...i didn't wanna take any chances ...my first 2 grows were phenomenal...