*PICS* Help with Kali Mist seedlings.. DWC + CO2

Got these two little ones under a 250w MH for now (will be on a 400w CMH as soon as it comes this week). They're in a DWC system, the reservoir is chilled, and CO2 is being added/controlled. The nute water is RO.

Here are the details:
Plants age: 3.5 weeks from germination
Nutes: GH FloraDuo + CalMag Plus + ProSilicate + Nirvana + B52
PPM: 980
PH: 5.7 (lowest it's been - it has peaked at 6.2)
Res Temp: 68f
CO2: 1200-1600ppm
Air Temp: 78-82f
Humidity: 45-55%
Light Distance 14in (light is contained in an air seeled cool tube)
Light Cycle: 24/7 lights ON

So it's a bit of an advanced set up, and this is my second grow, so there are lots of variables in play. I'm pretty sure the problem lies with the nutrients, so I'll start there.

I germinated with 100PPM of FloraDuo, and started the the full nute regimen at 25% strength for all the nutes once the second set of adult leaves began to show (about 300ppm). I forgot to add CalMag in the first dose of nutes, so I added it directly to the res in between the first dose, and the second dose of nutes.

By the time the third set of leaves were coming in, some minor, interveinal necrosis began to show, and I added another 25% of the recommended dose of nutes. Growth seemed to resume normally. This brought the ppms up to about 650ppm

After another four days, I added a third 25% of the recommended doses for all the above mentioned nutes, bringing the res to about 980ppm. It's worth mentioning that the three incremental additions of nutes were added directly to the res, as only a few root tips were touching the res while the lid was raised.

Both plants have had paling between veins, and brown spots since their first set of adult leaves. No signs of burning (ie. the discoloration/damage is largely relegated to the interior of the leaves), but it's still a definite possibility. Today the leaves on one plant started to droop, and both plants leaves feel somewhat dryer than they should.

It's worth mentioning that the roots are a bright white, and look great.. the res solution is well aerated as well. It looks like a hot tub with the bubbles turned on in there

Hope this is enough info, hope someone can help me get to the bottom of this! Thanks in advance.

Bob

heat stress, remember it's alot hotter under the light then in the rest of your room.. just back your lights off a bit and you'll be fine

Max, thanks for the reply. Is this pretty obvious to your eyes? It's in a small tent, 2'X2'X5.5', and there is a temp probe right beside one of the plans which rarely goes above 82. The light itself is in a cool tube, which I can touch with my hand perpetually. With the CO2, I would have thought those temps would be ok. Are plants that size typically more heat sensitive than adults? All of that being said, I turned my digi ballast down to 150W earlier today, and they're starting to perk up again, so you definitely seem to be on to something.

Love your signature by the way. Rise up!!

To be sure just back your lights off a tad for a couple of days and see what happens. I'm pretty sure kali mist is sativa dom and might be a little sensitive to food. Is that your ppm before or after adding all your additives? Also keep an eye on your bulb when using the dimming feature, if you keep it dim too long then it can ruin your bulb.. Its happened to me once and my cousin too even after I told him not to do it lol And we are using 2 different brands of ballasts. I'm pretty sure that most bulbs are meant to burn and that wattage they are rated for.

Thanks for the advice on the light, I'll back it off instead of dimming for sure...
The plant is getting 75% of the recommended dosage of all nutes, so that PPM value includes all the additives.