Red tiger lotus with thin leaves

[kagentx]

I bought this plant as a bulb, and now it has been growing leafs that are thinner than paper. Is it calcium i'm lacking? because my test kit are not able to read gH for some odd reason. I have one of those taverine rock that should release calcium carbonate and epsom salt which i dose with 1 tsp every water change for my 50 gallon tank (what is the exact dosage?)

I have 115 watts over my 50 gallon tank
pH6.6
kH 2 degree
nitrate 10ppm
phophate 1ppm

thanks for your help!

 

[savga]

The leaves are naturally pretty thin, but potassium deficiency can also lead to thin translucent leaves.