Is this an Mg deficiency? Plants less than 2 weeks old. (pics)

Hawk · #1 05-11-2008, 10:48 PM

I've got three plants. #1 is 11 days old. #2 is 9 days old. #3 is 7 days old. #1 and #2 are hurting and I'm not sure why.

--Temps are 76-80 deg. 35% humidity
--Light is ~200w of mixed spectrum CFL. Started at 3 inches away. Moved to 5 inches today.
--Fan is blowing on them. Sort of blustery at first but have since rearranged the airflow so they leaves don't flutter too much.

--All were sprouted in peat plugs and then the plugs where planted in soil
--#1 and #2 started in Sta-Green Moisture Control potting soil. It does contain fertilizers. #1 and #2 were transplanted into Roots Organics soil a few days ago. #3 started off in the Roots soil.
--I've alternately watered with un-pH'd distilled, pH'd distilled, un-pH'd tap, and ph'd tap. I can't decide what water to use because I'm ignorant about what's best. Runoff seems to consistently come out at 5.0-5.5. Water in has been anywhere from 6.5-8.5 in an effort to adjust the runoff pH (which hasn't worked well). I'm using PH-UP and PH-DOWN to adjust pH.
--I've tried to be sure not to overwater. But it's hard to judge.

Plant #1 (oldest of the three)--first and fourth pics--had it's two largest leaves start to curl down and turn brown/grey and die. This started 2 or 3 days ago (before the transplant). But it seems to be continuing even after the transplant. I think the transplant was hard on it. It's gone kind of pale and wilty looking since then. I was kind of rough on the roots trying to get all the Sta-Green out of there.

Plant #2 (second oldest)--second and third pic--has small brown/tan spots on its two bigger leaves. And the edges have just begun to curl up. Other than the spots and curling it seems ok. It's growing. It transplanted fine but I did leave more of the Sta-Green around the roots than #1.

Plant #3--last pic--seems to be fine. But it's also the youngest and was never in the Sta-Green [sic] soil.

I've been searching old threads for hours. I'm still not sure what to do. Mg deficiency seems the closest match I could find but I could be way off on that. Or I'm thinking it could be nute burn from the Sta-Green soil. Does nute burn continue in the plant for some time even if the offending soil is removed? Also, I'm concerned my runoff pH is in the 5-5.5 range (I'm using droplets to test). It should be about 6.5, correct? Should I add dolomite lime to the soil? Can I just PH-UP my water by a bunch to get the runoff pH to go up? Is this purely a pH problem?

Thank you for any help. This is my first grow.

skunkdog · #2 05-12-2008, 02:45 AM

dont over think it. they are weeds and your weeds look ok,

i would use distilled water, if your distilled it yourself, other wise let water sit in an open
bucket for 24hrs or so. to remore that shit they put in it,( forgot what its called),

when potting or re-potting mix dolomite in your soil

what will u be feeding them with?

Hawk · #3 05-12-2008, 03:41 AM

Thanks. I do tend to over think such things. Just want this whole experiment to turn out ok. I'm about to pull the trigger on a modest HID setup (250w) which will include running exhaust ducting through my attic. It's gonna be a major PITA to setup but I figure anything worth doing is worth doing right. But the health of these plants has me second guessing the whole plan (sort of). I don't want to drop a bunch of coin and effort on a project I suck at.

I don't know what I'll feed with. Any suggestions? I've got a hydro shop that seems to carry a reasonable selection. I'm still a couple weeks away on feeding though, right?

Snake · #4 05-12-2008, 04:21 AM

Since you mentioned possible Mg deficiency I'll tell you my recent serious problem with it. I had no leaf problems for the first 3-4 weeks of growth and had planted in Sta-Green container mix (with time-release nutes). I watered each time with distilled water since I didn't trust my tap water. When I started veg nutes 2 weeks in I used Miracle Grow's all purpose plant food (high in nitrogen) starting at 1/8 strength and building to 1/2 strength over time.

Right about the time I switched to 12/12, an HPS light, and bloom nutes (4 weeks from sprout) I noticed a few upper fan leaves with their edges curling upward, and some yellowing with rust-colored spots forming on the leaves. I misdiagnosed this as having my light too close and kept raising the light to try and solve the problem as more and more of the lower fan leaves started yellowing and getting the rust spots. At that point I started looking at my fertilizers and noticed that neither the veg or bloom versions I was using had any Mg or Ca. I had put some pelletized dolimite lime in my soil initially, but not nearly enough and the wrong type (couldn't find the dolomite flour). My leaf problems were described exactly by a Mg deficiency.

Since I had been using distilled water from day one (pH'ing the watering solution each time after adding the nutes) I inadvertently caused the Mg deficiency which, by the 3rd week of flowering, had gotten to all of the main branch fan leaves and was spreading rapidly. I was able to get some Mg-sulfate (epsom salt) from the local nursery and solve the problem (took 4-5 days to recover), but once it started it spread very rapidly and cost me 2/3 of the main branch fan leaves.

Next time I'm going to grow in a soilless mix and use "complete" fertilizers to avoid the problem. If you don't have Mg in your nutes make sure to use Mg-sulfate regularly to compensate, or better... switch nutes, before the plant gets to the 3-4 week point.

Hawk · #5 05-12-2008, 05:00 AM

Thanks for the input, Snake. I thought maybe Mg deficiency because of the spotting and edge curling. My plants seem awfully young to be exhibiting that though. But really I'm only speculating that a young plant wouldn't be susceptible. They have had some tap water which I believe is quite hard. But I haven't been able to measure the dissolved solids yet.