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