Blackenin leaves

hey guys whats up? anyways right to the point. I had this problem last year and i guess its back again. My plants tops keep on turning blackish discoloration which makes the leaves feel crispy. I posted this last yaer but i dont think any one knew the prob, i can post a picture if needed. I think its my water because last year i thought it was the soil i used but this year i bought pro - mix. Its kinda urgent so any help would be awesome

Ps. on a sadder note, i had 2 young ones drown to death. May they R.I.P:(

also they seem to be curlin down( i think)

thx

yea some pics would be helpful