Potassium Deficiency

[stu40]

Hi, i'm noticing some Potassium deficiency

No co2, dry ferts once or twice a week,40Gal tank potassium nitrate (¼ tsp) & monopotassium phospate (1/16 tsp) & trace

which dose would it be better to increase? KNO3?

Thanks

 

[SO19Firearms]

KNO3 would be best is the short answer
Have you got pics? A potassium deficiency is pretty rare I think, more found in aquaponics...

 

[stu40]

cheers.
will take some pics tonight.Only the H.Corymbosa is showing probs. Thought it was K because it starts as small holes that get bigger.

 

[ian]

That can also be a C02 problem.

 

[SO19Firearms]

That can also be a C02 problem.

Without seeing pics I'd lean more towards co2, especially if you dose KNO3 and KH2PO4. If you've got dark veins on the leaves as well as yellowing/pin holes, maybe K.
Chances are your lights + ferts are running the plants slightly too fast for no co2.

 

[stu40]

thanks for the help fellas, sounds like co2 issues are more likely then (especially considering pic #3)
i can live with that.If nothing else, i've learnt something new today

not the best photos but

was trying to hold the leaves with one hand, whilst taking a shot one handed & not drop the phone into the tank

 

[ian]

yep it looks like a C02 deficiency to me.

 

[SuperColey1]

That can also be a C02 problem.

Without seeing pics I'd lean more towards co2, especially if you dose KNO3 and KH2PO4. If you've got dark veins on the leaves as well as yellowing/pin holes, maybe K.
Chances are your lights + ferts are running the plants slightly too fast for no co2.

+1. More likely too much light to use with no CO2. Shouldn't really need to be adding ferts more than once or twice a month on a non CO2 setup (with applicable lighting) and most definitely not need to add K when you are already dosing as you are.