hello ..after 2 weeks.... the new leaves turn yellow and after that the end of leave begin to burn (i use only water) .tell me what's wrong...

i man use soil....a good pH....air extractor
..........that is not my first growing.

i turn mad

could be lack of nitrogen.. maybe you need to use some ferts. if its an emergency i guess you could mix your piss in their next water.

Why not start out with a good soil mix in the first place? For your next grow, here's a good mix:

2 parts Schultz's "Potting Soil Plus."
1 part Perlite.
1 part Vermeculite.
1 part Worm Castings.
Add to the mix one SMALL handfull of granulated dolimite lime.

Mix it all up well and off you go to grow prized pot plants.

You won't need any fertilizers for the first 45 days with this soil mix.

Vi

Grow Marijuana FAQ, Cannabis cultivation - marijuana growing tips & photos