Hey.
Sometimes the Biobizz allmix is a little hot (too many nutrients) for seedlings, that may be why the edges are going a little crispy. I've used allmix for my first grow, and still got some nice plants.
You really could do with a PH meter - it's super important to get the watering right. Although Biobizz say you can just chuck water in the soil and it "buffers itself" to the correct PH, It never seemed to work for me.
This means you need to know what the PH is when it's going into the soil - and take another reading and see what it's like coming out - then you can work out the soil PH with the following guide by Goauto
Rough Calculation Guide By Goauto:
Here's some good info on ph.....
If your runoff pH is higher than your starting pH, use this equation to determine your soil pH:*
Soil pH = Runoff pH + Difference
If your runoff pH is lower than your starting pH, us this equation:
Soil pH = Runoff pH - Difference.
For example, say your the starting pH of your solution before it goes in is 6.5 and the pH of your runoff is 7.0. The difference is +0.5, so using the above equation:
Soil pH = 7.0 + 0.5*
Soil pH = 7.5
If your starting pH is 6.5 and your runoff is 6.0, your difference is -0.5 and using the above equation:
Soil pH = 6.0 - 0.5
Soil pH = 5.5
So without a PH pen - you're kinda just guessing which will always be a bit hit and miss (alot of the time, its a miss)
I can recommend this one
http://www.growell.co.uk/essentials-ph-pro-meter.html -= it's expensive-ish, but is worth it's weight in gold.
Don't put nutes in the soil yet buddy

you're allmix has enough for at least 30 days... maybe more. When you have yur PH under control and your plant goes back to being a nice green colour, you will be able to guage when your plant needs a feed by the colour of the leave (but that only works if you've got the soil PH sorted, otherwise you could just be looking at the plant suffering becuase it can't take the nutrients in the soil, because the PH is in the wrong range).
I probably made that sound more confusing than it really is - once a few basics are down, it's all easy street and you're good to grow ^_^
Hope this helped a little
Blue
edit.. for future grows, if i "had" to use a soil straight from the bag - it would be Biobizz "Light" mix .. it's just a lot kinder on seedlings
Double edit .. Saw the tap water comment - I used to use water straight from the tap and it wasnt good. I now let my water sit out for at least 24 hours to de-chlorinate it, then i would adjust the PH to 6.4 ... if you have water left over for your next watering, don't forget to check it's PH before watering again, as usually it will creep up a few points over a day or so
