I can't tell from the pic if it's severe over watering and rot or there's no roots and its rot or a severe case of spider mites... either way that clone looks beyond help.... seed may come back.
kill everything, throw away, CLEAN EVERYTHING!! with h2o2 or bleach even use isopropyl on the equipment etc..
before starting again..
or you’ll never be successful..
you need the basics at least!