sickly shrivelling plants

[sage]

One of my plants is just not growing to the extent of my other two. It is developing as many nodes but the stem and leaf size is of this plant is considerably smaller than my other two. I'd say the stem is about 1cm caompared to at least a 2cm diameter stem in my other plants. The leaves are probably a third of the size of the of the leaves in the other plant. The other thing is the leaves are very shrivelled and dark green in colour. The pot is nearly always damp to so I think it may not be absorbing water. I treated with a soil pesticide which didn't do much although the bottom leaves seemed to be a little healthier as they grew in but to be honest this did nothing to the overall condition of the plant. I'm adding some photos of the plants so anyone can compare for themselves. If the plant looks healthy to you in the pictures this is an optical illusion

The first two pictures are the sick one and the third and fourth are the two healthy ones

 

[sage]

Soory heres the photos

 

[Mutt]

1. how often are you watering the potted plant?
2. Do you know your PH?
3. What ferts are you using?
4. Whats the blue stuff?

Sorry to answer questions with questions. but need to know to be able to trouble shoot.

 

[sage]

Mutt i had been watering the plants every day but have now cut it back to every second or third day.To be honest the compost is never really dry when i water it. Just doesn't seem to absorb that much water at all. I have never given it a ph test.Just used some compost i bought in a garden centre, don't know what type it was. As you can tell this has been a very amateurish attempt at growing weed! I have used plant food liquid fertiliser which is a mostly nitrogen fert. The plants are 8 weeks old and i have used it twice.
Hope this helps in the diagnosis. the blue things are slug pellets by the way