So I'll give you a run down of the tank . Going for a low tech tank. 60l - 24x12x12 Lighting - 20w 9000lumen floodlight ( roughly 8 inches above the water line) Substrate - ocean free aqua gro. Filter - aqual 400l/h connected to a sponge filter. I've having issues with the bottom of my plants dying . I'm not sure if I've planted them too close together or if it's a lighting issue . They are growing slowly but the top half looks good but the bottom half seems to be dying off. The photo is just one example . Any ideas ? Should I split my plant mass up ?