Why are my older leaves doing this?

21 days old. In veg. 50% full line fox farm. Dwc. Hydro guard full strength. Cal mag 1.5 tsp in 3.75 gallons. General hydroponics rapid start 1/2 tsp in 3.75 gallons, was doing 1 tsp for first 2 weeks.
Ph stays between 5.5-6.2
Led 2000 watt. Temp night 60-65F, day 75F. 18-6 light
Topped once, start LST today
Ppm currently 700 as of yesterday. Was ~500 during week two. And 200 during week 1.

A few of the earlier leaves started getting circle brown spots in the middle of the leaves. I added more cal mag, was doing 1/2 tsp. It didn’t fix the issue. Calmag brings ppm to 135-150 before adding nutrients.

For the 10,000,000 time on this forum if you want advice from the experts take a picture under normal lights.

mastermeow said:

21 days old. In veg. 50% full line fox farm. Dwc. Hydro guard full strength. Cal mag 1.5 tsp in 3.75 gallons. General hydroponics rapid start 1/2 tsp in 3.75 gallons, was doing 1 tsp for first 2 weeks.
Ph stays between 5.5-6.2
Led 2000 watt. Temp night 60-65F, day 75F. 18-6 light
Topped once, start LST today
Ppm currently 700 as of yesterday. Was ~500 during week two. And 200 during week 1.

A few of the earlier leaves started getting circle brown spots in the middle of the leaves. I added more cal mag, was doing 1/2 tsp. It didn’t fix the issue. Calmag brings ppm to 135-150 before adding nutrients.

Click to expand...

Better pics next time under reg light .
Brown spots look like a Phosphorus deficiency.
Suggest cutting the hydroguard to 2ml per gal and the cal mag to 2ml per gal
Ppms are hot to me suggest cutting back to 500
2k led is that like 3-4 feet away? thats alot of light on a little plant.
looks N heavy also

Excessive salts restrict plant growth

Looks like Wrong Ph to me (too high).
But cant rly be when u write ph stays between 5,5-6,2 which should be pretty perfect, so idk what causes that

As above. ph too low maybe? Did you add some ph down to much to quickly?

Not that it's related to your issue but you should tey to keep your day and night temps closer if you can. Beyond a few other things it qill keep the spaces between internodes closer.

myke said:

As above. ph too low maybe? Did you add some ph down to much to quickly?

Click to expand...

I cut my ppm in half. I checked it today and it was 1080. I have the ppm at 530 now. Ph is currently 6.1

Bernie420 said:

Better pics next time under reg light .
Brown spots look like a Phosphorus deficiency.
Suggest cutting the hydroguard to 2ml per gal and the cal mag to 2ml per gal
Ppms are hot to me suggest cutting back to 500
2k led is that like 3-4 feet away? thats alot of light on a little plant.
looks N heavy also

Excessive salts restrict plant growth

Click to expand...

I added 1/2 tsp of open sesame from fox farm last night. Today I checked and it was worse. The ppm shot up to 1080. I brought the ppm back to 530, ph currently 6.1

mastermeow said:

I added 1/2 tsp of open sesame from fox farm last night. Today I checked and it was worse. The ppm shot up to 1080. I brought the ppm back to 530, ph currently 6.1

Click to expand...

Right on even at 530 that might be too hot 400 might be a better number to shoot for if possible since they are small. when they are too hot they dont grow,,, in a couple of days you should see them gowing or perkier .

for me, clones are about 250-300 little veg 350-450 big veg is 550-650 and flower is 650-1000 and I use 1000wat hps bulbs.

I dont know what open sesame is so cant comment on it.

It might be more than a few days since they are stressed from the hot nutes so patience might be needed before you make changes again.

a little b vitamins might help for the stress if you have any but not absolutely needed

myke said:

As above. ph too low maybe? Did you add some ph down to much to quickly?

Click to expand...

I think you missed what I mean.
Ive added ph down before to my res ,im in rdwc. so what happens is ph of 3 or so goes into the feed line over the plant.Causing the spots.

are those wood screws in your lid?

Switch to RO water then aim for 500 total. Looks like toxic salts buildup and will only get worse.

What's the ppm of your water?

Normal light pics if you want better opinions. Or use the flash after light's out.

myke said:

I think you missed what I mean.
Ive added ph down before to my res ,im in rdwc. so what happens is ph of 3 or so goes into the feed line over the plant.Causing the spots.

are those wood screws in your lid?

Click to expand...

That makes a lot more sense. I add the ph up/down with the tube and blow it in. And yes, they are wood screws. Ghetto but worth it. I may be down the 2 plants soon. I flipped today with ppm 600-720 between the 3. That one was never healed all the way but the other 2 hit the net. Day 28 rn. I’d keep it in veg longer but the tent is only 5 feet. 2 should fill up the tent fine if she doesn’t get better soon. Half the size of the other two. Accidentally topped her when fimming