So i just got some amazon swords and staurogyne repens about 4 days ago and now both plants have this brown/black stuff on their leaves. I don't know if it's dirt from when i dirted the tank and it settled on them, or if they are dying. I'm using a 6500k 40watt cfl about 17 in. above the plants. Is it not enough light? Too much? I've also dosed twice with co2 booster(api) and was going to use it every 2-3 days. All my water parameters are back to normal. I'm new to planted aquariums so any thoughts will help me greatly.