everybody here usually dont mind helping but you really should post ALLOT more inf on your situation, things like
system (assuming your in hydro)
size of cube
do you have light on it
what kind of light
moisture of the cube
is it in a humidome
things like this will get you allot more responses allot faster. not sure for the ppm's of a super silver haze (assuming again this is the seed you are cracking not sure though) but dont feed untill you see roots out the cubes (depending on size of course) good veg is to start slow like 1/4 strength nutes and up from there every week or so. ph in hydro (assuming again you are in hydro) should always be around 5.5-6, i like to let my ph swing up from 5.5 to 6 in veg in a week until the water change it allows for more available nutes to be absorbed, in flower i like a stable 5.8.