DWC AUTO's - LEAF CURL AROUND EDGES

Here's the setup:

• Closet Grow (3x5)
• 3 Auto Strains (Purple Cheese, Max GOM, Pineapple Express)
• 150w HPS (yes i know, I'm upgrading to a 250w hps in the next day or two)
• 3x DWC 5gal bucket, 10" basket w/ air stone for oxygen (this is not recirculating)
• Ventilation is a portable AC unit, exhausting into attic, creating a vacuum under closet door acting as an intake. The air blowing from the A/C unit also acts as a fan to circulate air (but I'm planning to get a small oscilating fan anyway to help)
• RH stays at 50-60. Temps due to AC unit stay constant at 75f. Water in rez stays at 74f

The plants are currently in their 4th week of veg. I have them at 5.8ph, 650-700tds using Dynagro Grow hydro nutes (I started them off at 450tds, week 2 550tds, week 4 650-700tds). Roots look healthy, leaves are healthy green, size and growth is good. No yellow tips on edges of leaves. No brown / yellow / white spots in leaves. Just on a few fan leaves of one plant has some upwards curling on edges only. What do you think this is a sign of?

I also use Dyna-Gro's Pro-Tekt and Mag-Pro at 1/2 strength per their feeding chart in combination with the Grow.

Any insight on what may be causing the upward leaf curling? The light is about 1 foot above the plants.

same trouble here need some help

I really don't know what caused it 100% but it never really affected the plants. First of all, I read in multiple places sometimes it's just a characteristic of the genes in that specific strain and nothing to really worry about. On the other hand, I still felt like it was weird. I removed my portable AC unit because it had a horrible auto mode. For example, I'd have it set to turn on when it got up to 78degF. It actually wouldn't turn on until it was like 85, then would kick on, bring the room down to 65-70, and then turn off, and repeat that cycle. That was making my humidity and temperatures fluctuate at such extremes I felt like it was negatively affecting the plant. Then again, my other 2 didn't have the problem, just 1 plant, but i felt like it was the cause of the problem. I managed the higher temps without the AC unit in the closet by drilling a 6" hole in my closet ceiling to the attic and venting through a duct I installed with a shitty fan.

Oh, one more thing, I upgraded to a 250w HPS, 150w was way too small for 3 in that space. I believe I also backed off a lil on the nutes and kept them around 500-600tds from that point forward until when I finished. They all turned out fine, decent yield, couldn't complain. Still enjoying it right now as we speak actually