hello, i have a few Staurogyne sp plants in my tank & all of them have a almost black susbtance on the leaves, the new plants that come through are ok untill they reach a certain size then bam "black death", this does not affect other plants. i have tried to scrape it off but its in the leaf not on it. tank stats 180 ltr 1 x 45w juwel nature t5 tube & 1 x 45w arcadia j5 plant pro both with reflectors standard 600lph juwel filter + tetra tech 1200 ext filter ph = 7.2 kh = 8 gh = 10 does anyone else use this plant? anybody had any problems? i dont want to bin this plant as it really is a nice plant, once established grows really well thanks in advance for any help. ps = would a pic help?