yeah the humidity is low, around 40% usually, but the heat is usually 80-85f. ac unit coming soon. is it safe to transplant them at that stage? i have kgrow fert with nutes and bigger pots ready to go.
Ok. My plants looked exactly like yours when they were that age. I had exactly the same environmental conditions as well. Here's what I think is going on:
You said it takes eight hours for the soil to dry out after a watering. I believe this is the problem. When your plants get watered, the soil gets completely saturated for a short amount of time until your low humidity and somewhat high temps suck the dirt dry. I also suspect from the straws that there is too much air movement for these skinny stemmed plants to handle. Too much wind can also contribute to the dirt drying too fast.
Another potential problem is that you may not have enough actual dirt in your pot. If you had a bigger pot, the top level of soil would dry, and the lower levels would remain moist for longer.
Here's my solution:
Transplant into it's final pot right now. It should be somewhere around 2 gallons or more. Be very careful not to disturb this stressed plants root system. Try to get it out in one piece.
After you transplant, water so that all of the dirt in the pot gets saturated and runoff occurs.
In 24 hours, water again. This time, only use the amount of water you were using when it was in the small pot, plus just a little bit more. Water only directly below where the plants leaves are, not anywhere close to the edge of the pot.
Do this again in 24 hours, maybe a little more water this time.
After that, wait something like 32 to 36 hours and water with a little more than last time.
Gradually(like maybe over a few days to about a week and 1/2) increase the amount of water and the time between waterings.
At the end of this process you should be watering about every 2 days, maybe every 3. You should be watering the entire surface equally, and it should be flowing out of the drainage holes. (measuring how much water you are using every time is an important step to providing a consistent watering schedule for your plants. I use about 1 gallon for my 2 gallon pot.)
Using this process ensures two things. First it addresses your moisture problem immediately, without causing undue stress on the plant that multiple transplants would create.
Second, this method of gradual increase of water prevents the new "unrooted" soil from rotting(rotting not rooting), which would likely occur if you were to saturate the entire pot at every watering from the time of transplanting.
Oh yeah. If I were you I would not try to separate these two plants. Just cut one off at the base so you don't have to disturb the other one.
edit: I do not think the cause of this problem is underfeeding. From the picture, the plant looks very young. You probably wont need, nor should you, use fertilizer until it is older.
I type for shit, so I'll blame it on laziness. 
