that's damping-off...pythium...
you need to start with a STERILE growing medium.
And replace the 400mh with a couple CFLs until they are big enough to give ferts to, about 3 weeks old.
oh and keep your humidity way down and don't overwater the seedlings.
stinkyattic Reviewed by stinkyattic on . I don't know what to do anymore!! My plants all keep toppling over!! Why do they do this? My 400W MH is like a foot above them, so there is no way that they aren't getting enough light. Any suggestions/ways for me to get to the "root" of my problem? Rating: 5