Hey seal.
Sorry I haven't been around. Things have been disrupted here.
Your girls are moving along and looking pretty good apart from the leaf curling issue. The BH seems to be suffering the worst. Different strains will react differently to stress. 29c is the upper end of the plants' comfort range. In itself it's not a problem but it will exaggerate the dehydration. Strangely, the fan blowing on the leaves (which is in general a good thing) also accelerate the rate of dehydration. This may be why the BH seems the most distressed.
At this point, I would be giving the plants 1/3d to 1/2 the pot volume of water every 2 or three days and a heavy watering, meaning enough water that it starts running out the bottom one every 4/5 waterings.
Well it's a dehydration problem and my guess is it's from *underwatering*. You say you have them in 5L pots and you are only giving 1L of water each time. This is very stingy for a pot that size. It would have been fine while the plants were small and the lights were weak. Small plants dont draw much water from the soil but as they grow they drain the pot faster and faster. I say again, it's much better to make this mistake than over watering but it's still a problem. The plant may also be outgrowing its pot which can make things tricky.
Here's what I would do:
First, take the BH out of its pot and look at the soil. I expect you to find the bottom half to be quite dry. Do this very carefully of course. Make sure the soil is moist but not wet. Work the pot a little with your hands, distorting the rim to break the sides loose from the soil. Put your hand palm down on the soil with the plant stem sticking up between your fingers, turn it upside down and with your free hand tap and tug on the pot until it slides off. This is usually easy to do if you are careful and patient and shouldn't bother the plant. Have your camera handy and take a picture of what you see. Then put her back and apologize for the indignity.
If, as I expect the soil is dry at the bottom, get a tub of water filled to about half the height of the pot and set the pot in it until it has soaked up at least two liters of water. You will want to measure the water you put in the tub so you know what a 2L drop i the water level looks like. Do the other two, refilling the tub each time.
Spray or mist the leaves with water until they are dripping like after a heavy rainstorm. A drop of dish soap will help the water wet the leaves.
Turn off the big cfl and the fan for at least 24hrs.
Cover the plants with transparent plastic bags.
You should see improvement in 12hrs and close to complete recovery in 24.
(its a beast)
