Trouble with curling leaves

[Dustin Perez]

I have a 55 gal and I've been struggling with the leaves on my alternanthia curling. I dose easy green 2 times a week, easy iron 2 times a week, and potassium 2 times a week. I keep nitrates around 20ppm kh is 5° gh is 9° and ph is 7.4 to 7.6. All the other plants seem to be doing fine minus some pin holes in the the potassium hogs. But I'm at a loss it's been about 6 months now and can't figure it out. Also I do not run CO2. I've been racking my brain. I've basically become a chemist/biologist with the amount of research I've done. Please HELP ME

[Mmiller2001]

It's most likely a lack of CO2, but curling can be Ca/Mg issue also. 

If your source water is tap, pull a water report and see what amount of Ca Mg is there.