Diagnosis help for a noob

Hi all,
I I've attatched a photo of the problem in question. I recently underwatered and stressed them out only 2 days ago, is that what's caused this maybe? It's showing on 2 different plants.
I was using a drip system but I was having watering issues, I've now got my 6.5L pots filled with hydroton in a DFT system with an added air stone.
The ladies looked so much happier after they're change of system, the roots are growing out the bottom of pot and into the water.

Ph is around 6.0 always.
Humidity is a bit low at 50% however it can't be helped.
Tempretures around 22°c lights on and 19.5°c lights off. (I'm waiting for a replacement tube heater will adjust temps when it arrives Monday).

Ppm 720 : vitalink calmag, Dutch pro grow a+b, Dutch pro multi total, Dutch pro take root.

Actual 200w Led viparspectra light (on 50%).
They sprouted start of Nov.

Please give me any tips that you think will help me it's my second go and still learning.
Its driving me mad but I'll get there soon....

Thankyou for reading.

PS: I know there's not enough space, I have another tent that's going up after my housing inspection.
Will flower 2 in this and the rest in my tent.

Identify the problem please. Or what you are concerned about.

The yellow marks on the leaves.....

Mattsmith1871 said:

The yellow marks on the leaves.....

Click to expand...

Those like physical damage to me. Not a fungus. Your PPM isn't high and you're giving calcium.

I'm not 100% sure, but there might be some mag def.

Here's a bit of a clearer pic...
I've been using hard water nutrients so it could be a possibility, I've been using calmag since the start maybe I need to use more will give it a try thankyou.
Looked to me like ph fluctuiations, it's not that tho I've been keeping am eye on the pH

Mattsmith1871 said:

Here's a bit of a clearer pic...
I've been using hard water nutrients so it could be a possibility, I've been using calmag since the start maybe I need to use more will give it a try thankyou.
Looked to me like ph fluctuiations, it's not that tho I've been keeping am eye on the pH

Click to expand...

Magnesium deficiency building.

hotrodharley said:

Those like physical damage to me. Not a fungus. Your PPM isn't high and you're giving calcium.

Click to expand...

They looked well under watered 2 days ago, they were clawing, one or two leaves wilted and looked as if they were overwatered, I'm not sure whether that could've caused it.
The system change should have sorted that out tho, maybe they still need time to recover?

Underwaterings a new one to me if that's what it is.....

hotrodharley said:

Magnesium deficiency building.

Click to expand...

I'll top up the calmag now, hm do u recommend per L?

Mattsmith1871 said:

I'll top up the calmag now, hm do u recommend per L?

Click to expand...

I'd spray foliar 1 tablespoon unscented epsom salts in a gallon of water. Add a drop of dishwashing liquid.

I don't have any of that to hand, the calmag bottle said 1ml per L should've just read the back! I put not even half that in when I mixed in my nutes
I just added another 15 ml so will see how it goes....
I didn't realize how import calcium and Magnesium actually was
Live and learn!

Mattsmith1871 said:

I don't have any of that to hand, the calmag bottle said 1ml per L should've just read the back! I put not even half that in when I mixed in my nutes
I just added another 15 ml so will see how it goes....
I didn't realize how import calcium and Magnesium actually was
Live and learn!

Click to expand...

I have got some ph 6.0 water in a spray bottle, do you think that would help or do harm?

Mattsmith1871 said:

I don't have any of that to hand, the calmag bottle said 1ml per L should've just read the back! I put not even half that in when I mixed in my nutes
I just added another 15 ml so will see how it goes....
I didn't realize how import calcium and Magnesium actually was
Live and learn!

Click to expand...

Calcium and Magnesium are antagonists to each other, so adding "CalMag" to deal with a Magnesium deficiency isn't always the best strategy. Epsom Salts are Magnesium and Sulphur, and can be purchased for a few bucks at any local grocery or drug store.

Will it be okay for a hydro system?
I added the calmag and I can see an instant improvement in colour so thankyou for the help.

PJ Diaz said:

Calcium and Magnesium are antagonists to each other, so adding "CalMag" to deal with a Magnesium deficiency isn't always the best strategy. Epsom Salts are Magnesium and Sulphur, and can be purchased for a few bucks at any local grocery or drug store.

Click to expand...

Then catch up with cal mag in your regular feeding.

Mattsmith1871 said:

Will it be okay for a hydro system?

Click to expand...

Yep.

Those pics by @Mattsmith1871 should be put in an index somewhere as classic examples of magnesium deficiency, particularly 1 & 2. Nice pics!