in my experience i have the same problem often as i use tap water in a hard water uk area, and cheap good quality compost, alot i make myself, i found using some feeds it wouyld burn, ive ended up with tomato feed, its cheap, has the right chemicals and is edible so when washed it leaves no taste, and the yields are no differnet from the 80 quid or 15 quid nutes i used, the water i advise to put in a bottle if tap, and leave stand with lid off for 24-48 hrs before use, this allows the chlorine which is a gas naturally to reduce by evaporatin, i found with this it reduces burn, laay off the feed for a bit, i always give half the reccomended dose to autos as they are such a small plant whichever you choose compared to a sativa say that could be 7 feet tall and 3 wide! reduce nutes or stop and purify the water, as long as its n the larger leaves dont worry, as long as you have a 60% or so healthy leaves this is enough for the plant to survive, we all give them mad haircuts near end and they live so a few burnt leaves wont hurt, experiment with water,nutes, dosage etc, you may find washing the plant with water for a week or two, then re introducing nutes at a half level will stop the spread, lose the tips of the burnt leaves with scissors if needed leaving the greenpart, this wont hurt, i often only water and feed once a week as in 6.5 lt pots they take that long to dry out, this actualy makes the roots stroner if you let it dry so the soil cracks from the side of the pot, but before the plant starts to wilt, watering less will also allow nutes to level at a lower level, this may help.
to add, i yield between 3/4 to 1 1/2 oz per plant every plant from all lowryder strains to mini guns, white russian. i uise 1x 600w hps 2x 400w hps in a seald sheeted room in a cold loft, size 2m wide by 10 long 25 autos each side.also have a 12/12 set up with big bud and thaixskunk #1 going under a 400w hps. using sat tap water and a 2 quid bottle of tomato feed, and 3 bags for a tenner soil, the trick ios, resaerch and experience, its taken 5 yrs to settle on my way, we all do it different as we all haver different conditions, plants set up etc, but its important to start with the right soil so you dont burn them, check the cannabis growers bible, which can be found on extra torrent as an e book, its just that the bible, tellsd you everything from breeding to curing to ph different soil types absolutely everything! but experiment with nutes, soil water to erridicate your problem in yoiur set up, it may take a few grows change 1 thing at a time, but when you crack it stick with it, your solution lies in soil/water/nutes as is a burn, but everyone diff so experiment untill acceptable, i live half a mile from my best m,ate with a the same set up( my old one and i set it uip for him) but over 3 yrs he has changed and now does it completly diff to me with same plants, but that works in his space and he sticks with it and yields the same, its finding the balance in your paticular set up and plant choice, but cheap or expensive, water soil and nute are vital, honestly, i cant say get the growers bible enough its full of exact info and as i say can be downloaded as torrent with bitcomet or similar from here
http://extratorrent.com/torrent_download/2630436/The+Cannabis+Grow+Bible+REALPDF.pdf.torrent
im the one person sharing it at the moment!
