Can anyone sort this out...

My plants are yellowing from the bottom up.
Growth is at a crawl, and I need some help!
My lights (250w) aren't the problem.
my temps are fine (25ish).
My airflow is adequate.
I think it is the soil. Its regular tomato soil (garden center).
I added no nutes and just clean water. (when soil is measured dry)
I believe the soil lacks Nitrogen (amongst other things)
What suggestions do YOU have?
Perhaps a common additive (bird poo? guano?)
Or maybe some diluted urine (which I did a few days ago - still no improvement)
Also added a little bit of sensi grow part A ( 3-0-2 or similar)
I have no other nutes available and was thinking that, although I may see improvement due to the small dosage of nutes I've given, I shall probably start a new lot with something added to the soil.
I used a similar soil a while ago and everything was good - using only big bud liquid during flower.
The white stuff is perlite. I use a little in the soil and a sprinkle on top!

HELP AND SUGGESTIONS APPRECIATED - THANK YOU!

Can i also point out that the bigger one is older and the others are a month old!
The strain is AK47 or the newest and current best AK - ?

your poor babies are starving. start out with a weak mixture of nutrients. I suggest foxfarm as they're all natural and less likely to harm your girls. You need to take care of this now or your plants will either hermie or go male. Stress is bad for marijuana plants.

they are just begging to be fed...keep feeding them with your sensi grow and if u do want to add something to the soil for nitrogen, my suggestion would be using guano.

can you suggest a non commercial alternative to add to the soil? A general thing thats cheap (guano?) UK grower says cheers! fast reply thanks! what ratio of it?

yes feed them asap....!!

Ok maybe some liquid nutes and or bat guano. How about bio-bizz ? cheap and effective apparently.
Any suggestion before I order Looking to spend about 10 pounds. Will liquid organic nutes be better than guano?
And what good might potash do?

not shure about that line of nutes but if you can get dyno-grow get that.

http://www.youtube.com/watch?v=CLVmuAsVza4 This looks tempting!
And this - http://www.growell.co.uk/biobizz-nutrients.html
Thoughts?

Urine is free and has lots of N. Do the pots drain well? Look for a NPK ratio close to 3-2-1 for veg and 1-2-3 for flower.

good simple advice - and now I think perhaps the organic canna stuff is a good long term vegging solution. With my big bud for flowering - I think I will be happy enough!