Discoloration on tip of leaf and spreading

Hi everyone.

This is a problem I'm having with my 1st grow. I've got two Nirvana Bubblelicious autoflower plants about 2.5 weeks from germination. One of my plants has a leaf with a discolored tip which appears to be spreading down the leaf. The rest of the plant is absolutely fine. I'm watering every other day sparingly, the soil is pretty dry on top so I doubt its over watering (Moisture probe into the bottom of the pot reveals moderate moisture, basically 50/50 between wet and dry). I haven't used any nutrients yet and they're under CFL lighting, temps are between 75 and 80, humidity is about 50-60%. PH is about 6.5-7

The other plant growing right next to it has no symptoms. Just this plant and just the one leaf.



Any ideas?

Well, its spreading a bit, the original leaf has more of the discoloration and has lost a bit of the tip. A couple more of the leaves on the plant have got a little bit of whatever it is on their tips (see pics). There is some leaf curl too. I started nutes at 1/4 strength with the last water but this started before the first feeding which made me think it might be a deficiency of some sort.

Otherwise than the obvious, the plant looks fine

Any ideas? I want to nip this in the bud, ahem

I'm guessing that the damage is from the leaves making contact with the soil, or edges of the pot. But, in the newest pics, there looks like there's some heat stress going on(curled leaf edges), which is a seperate problem. Also, I know this might sound like stupid question, but I have to ask, just to make sure,lol....did you PH-adjust the fert, before adding? I'm asking because the temps sound perfectly normal, and am thinking that the curling might be caused by low PH. Did that curling start after you fed them?

The plant in the pics is directly under a 75w (actual watts) cfl and sharing light from another 105w and a couple of 20w warm light cfls but putting my hand where the leaves are is just slightly registering warm. The curl was happening before I started feeding the plant. The soil is a steady 6.5 now, could that be cause for concern?

The bizarre thing is that right next to this plant is an identical one, same soil, lighting, watering and so on and it has slight leaf curl but no discoloration as this plant does.

Could under-watering cause these symptoms? I water every few days when the pots feel light and are very dry. When watering, should I water till I see water running through the bottom of the pot? (I'm not doing that at the moment btw), just till the pot is heavy-ish again.

Perplexed

^Yes, you should be watering heavily, when you water, that's always a good thing. Other than that, everything sounds okay, which makes it tough to identify your problem. Hmm.... *needs to brainstorm a little longer*lol

Thanks for the responses so far jawbrodt. They'll be due for a water in the next day or so and I'll water them till I see some runoff.

Just a quick update. Gave the plants a good watering and 1/4 strength nutes and I think we're back on track. Discoloration has stopped and the plants have exploded Also added some extra air flow and increased the humidity in the room.

Heres the latest pics of the buggers 1 month from germination.