[The_Skunkist]

When you turn a powerfull light on 24h/0 .You always have to be super aware about (sometimes severe) CAL/MAG deficiencies .

That's why 24/0 light cycle is not so recommended .
If you use them in mono nutrient it's 1 part of Mg for 2 part of Ca.

And for sure, all the other nutes have to follow .

Are your plants growing faster and bigger under cMH ?
So more Ca and Mg and nutes (than your habits) is logical .

Most of the nutes supplements or "boosters" on the market are N - Mg - Ca complexes .

I hope it helps .

[Zeez]

Has your PH meter been calibrated lately?

[ambertrichome]

4ft for 400w IMHO is way to far from the plants.

I start seedlings under 1000w Hortilux HPS at 24 inches in a 4 x 4 area. I'm not using RW, but that not important.

Id watch out for excess drying, and lower the lights. Lowering lights will also make it dry out faster of course.

A 1000w Hortilux/HPS puts out 62.5w sq/ft at 24 inches and 4 x 4. In veg/flowering I can get them 18-20 inches with good airflow.

I almost always use a 24 hours veg cycle.

In chemical gardening, I use 20% of recommended dose of Fert, and Water/Feed Everytime, in Both Veg/Flowering. Seedlings get half of that, starting at the second watering, after they pop the soil, so I never get any deficiencies.
I rarely have to skip a Feeding with this watering scheme, but its something to watch out for, and is not out of the question.
With my tap water I use 1tsp Magnesium per 5 gallons water

[samiam]

Okay guys well now im getting tacoing leaves.
My humidity is at 60% with 75f temps.

The same mother plant is doing fine under MH. All these problems started when I switched the lights to CMH.

Are they still just trying to adjust to the CMH lights?
I'm not sure what else I can do.

[Snook]

Originally Posted by samiam

Okay guys well now im getting tacoing leaves.
My humidity is at 60% with 75f temps.

The same mother plant is doing fine under MH. All these problems started when I switched the lights to CMH.

Are they still just trying to adjust to the CMH lights?
I'm not sure what else I can do.

go back to the MH, see what happens..

[Spaventa]

Originally Posted by samiam

Okay guys well now im getting tacoing leaves.
My humidity is at 60% with 75f temps.

The same mother plant is doing fine under MH. All these problems started when I switched the lights to CMH.

Are they still just trying to adjust to the CMH lights?
I'm not sure what else I can do.

Coincidence and causation are often confused. This has nothing to do with your light. Its probably feeding, possibly due to ph or an issue with root environment.

[iTarzan]

Hey skunkist can you link a thread or article. I have run into unexplained cal/mag symptoms that went away. I did stop 24 hr light too but I didn't know about this.

[samiam]

I adjusted my pH down to 5.5 from 5.8. I pulled one out of the pot and all the roots are nice n white no sign of root rot or bugs in the roots or leaves.

I will add the plants are growing much faster under the CMH vs the MH.

[Spaventa]

Did you calibrate the ph meter as suggested by zeez? I would. What nutrients are you using, sorry if you said already I don't see it.

The more likely cause of deficiency when you been feeding plenty, is toxicity. For instance too much potassium will lock other nutrients out so the visible symptom of K toxicity is Mg, P and eventually N deficiency. You get taco leaves with Mg so maybe look at that

Other thing is that when problems appear, they didn't just appear something was going wrong before you changed the light. The only possibly of any causation could have been the increased useable light raised the metabolic rate and problems showed up more - raising the game will expose any weakness.

[WHIPEDMEAT]

3 main reason can cause it,
ca- mg deficiency
heat and humidity stress with overwater
or some parasites aphids i think

look the leaves closer that can be clue if this comes from imbalance of nutes you may notice discoloration on the leaves