Curling Leaves

[Bgssamson]

I have a curling on lower leaves. Is it pottasium or calcium deficiency?

55g planted with Ecco
- 4 watts per gallon
- 50% weekly water change
- Pressurise Co2 2-3 bps and DC is green to yellowish
- Kh2po4 (M-W-F) = 1/4 tsp
- Kno3 (M-W-F) = 1 tsp
- CSM+b = (T-TH-Sat) 20 ml


Should I add K2SO4, if so how much?

-Brian