I don't know what "NTD" is. Could you explain?
Ammonia is 0, nitrite 0, nitrate's at about 6, pH 7.6.
Aren't these where they are supposed to be? Am I underfeeding them? I do a 25% pwc once a week. The other fish seem fine: 2 clown loaches, a big pleco, a dwarf angel, a dwarf frog, 2 ramshorn...