Leaves cupping/canoeing up

My oscillating fan broke 6 days ago (only managed to replace it yesterday) and about 2 days later I noticed the leaves started cupping only on my White Rhinos from GH. My Early Widow and the plants I started from bagseeds are looking fine.

I'm using a 600W HPS which is about 2ft from the top of the plants.
I have an oscillating fan on low blowing air at the plants which are now 26 days old and still vegging. They're still growing albeit slowly.

These pics are 3 days old but they're looking about the same with some of the leaves' tips turning brown. The lower branches are still getting bigger though.



Now this is my Early Widow:


And the plants I started from bagseeds:


Their leaves seem to be starting to cup a bit too in those pics but they're looking better now and it was really slight anyway.

Do you think the cupping is really caused by heat stress?
I'm really clueless right now, I really don't want to lose my plants

might need to transplant into a bigger container. They look right for their age, I wouldnt worry about it much.

I don't think that's the problem, I'm not sure on how big the pots are but I'd say 5 liters or something along those lines.
I'm thinking about switching the light cycle to 12/12 in 2-3 days once I buy clonex so I can take a couple of cuttings but I'm hesitant because of how the leaves are looking.
On one of the plants the top leaves' edges are really starting to look brown and burnt and the other plants are looking about as bad as the one in those pics :/

Oh and the affected leaves have an uneven color and feel kinda crispy.

im not sure mate but does this mean they are thirsty when they do that?

From the research I've done the plants usually do this in order to conserve moisture.

Bump.
They're looking much worse. Please help me

It is a combination of under watering and/or heat stress.

transplant them, and dont even think of cloning them yet there way to young might kill em if you do
as well raise your light up about a foot or so, when you water do you water the leafs if so stop just water soil STAY AWAY FROM LEAFS

TRY doin a flush on one plant as well lower your ph to 6.2

DrFever said:

transplant them, and dont even think of cloning them yet there way to young might kill em if you do
as well raise your light up about a foot or so, when you water do you water the leafs if so stop just water soil STAY AWAY FROM LEAFS

TRY doin a flush on one plant as well lower your ph to 6.2

Click to expand...

Yeah stress em out some more with a transplant while they are already stressing. Great advice!!!

bigv1976 said:

Yeah stress em out some more with a transplant while they are already stressing. Great advice!!!

Click to expand...

well beats sitting there letting them wither away i tranplanted many plants in all stages of growth an never had them stressed out got larger pot added soil wetted it and then cut the other pot then put complete soil and plant on top of soil added all round watered and worked out great


dude i just transplanted 2 nights ago from FFOF to MG organic and the plant is acting like its alive and awake now...almost thanking me haha look at your quote lol

Thanks for the help guys, +rep

I'm pretty sure it's not under watering, I've been watering every 2-3 days when the soil starts feeling dry a couple of inches below the surface. Also, I water the soil, not the plants themselves.
I just raised my light about half a foot and put the fan on medium instead of low.

I'll borrow my friend's pH meter tomorrow and post the water and runoff pH.

Anything else I should do?

DrFever said:

well beats sitting there letting them wither away i tranplanted many plants in all stages of growth an never had them stressed out got larger pot added soil wetted it and then cut the other pot then put complete soil and plant on top of soil added all round watered and worked out great


dude i just transplanted 2 nights ago from FFOF to MG organic and the plant is acting like its alive and awake now...almost thanking me haha look at your quote lol

Click to expand...

Hey just to let you know smart guy my quote is from a current test grow in which MG is far out performing FF. FACT. You dont know what you are talking about dude. This guys plant is very obviously heat stressing and you reccomend he transplant. That is stupid. Then when I call you on it you try to look smart again by trying to take a shot at a quote from an actual fact based thread that maybe you should read. In fact maybe you should do alot more reading before giving out advise and helping fellow noobs kill their plants. Leave the advice to people that know how to grow bub k?

DrFever said:

transplant them, and dont even think of cloning them yet there way to young might kill em if you do
as well raise your light up about a foot or so, when you water do you water the leafs if so stop just water soil STAY AWAY FROM LEAFS

TRY doin a flush on one plant as well lower your ph to 6.2

Click to expand...

Taking cuttings will not kill a plant, however transplanting a plant that is obviously under stress is not a bright idea. Your advice about watering or wetting leaves is off as well, as the plant isn't showing ANY signs of spot burns. Foliar feeding is beneficial, however, where does the OP even mention that he does this? Your advice is all over the place, yet fails to address the plant's symptoms.

The only time a leaf will cup like that is for one of two reasons only, one is heat stress, lack of water. The other is a Mg deficiency which is caused by a PH below 6.4 in soil (in my opinion, DrFever's sugested 6.2 is closer to a hydro PH than it is soil), or from using RO water for feeding and watering, or from using tap water with chlorine in it, in which case you want to add some Cal-Mag if using liquid ferts, or Epsom salts if you are growing organically.

You stated in your OP that the 600 watt is 2 feet above the plant tops. Don't raise it any further as suggested by the Fever, as you'll only be dissipating additional light. 2' is plenty high enough for a 600w. I prefer 12", but I'm air cooled. If you need to raise the light higher than 2', better take a look at your ventillation and heat build up issues.

Good luck

Thanks a lot for your great response Serapis, +rep.
I've been watering with tap water which had been stored in 5L bottles for at least a few months, I just replaced the water on all of them and I'm gonna let it sit with the cap off for a couple of days for the chlorine to evaporate. I'll measure the pH tomorrow but it's usually around 6.8 here.

bigv1976 said:

It is a combination of under watering and/or heat stress.

Click to expand...

Look no further.

DrFever said:

well beats sitting there letting them wither away i tranplanted many plants in all stages of growth an never had them stressed out got larger pot added soil wetted it and then cut the other pot then put complete soil and plant on top of soil added all round watered and worked out great


dude i just transplanted 2 nights ago from FFOF to MG organic and the plant is acting like its alive and awake now...almost thanking me haha look at your quote lol

Click to expand...

I had similar problem.. my bk
didnt even flinch wen replanted..no wilt nothing !!! Just grew a third almost overnight... some plants must love the stress..idk

4 out of 12 plants from seed exhibited this canuing of the main terminal leaves. I increased airflow with a lower temperature, by raising the light and turning the fan a notch higher. 3 out of 4 are males, so I have altered the climate for 1 female...