just a guess but that soil looks to be quite wet an compacked i would not water it for a week or so until you can stick your fingers about 2 inches deep an it feels moist not wet,just out of curiosoty how much are you watering/feeding etc,best bit i think you can do is dig the plant out best you can without damaging root structure buy a new bag of compost that has some nutes already init check your drainage holes in the bottom of the tub if only 1-2 put about another 10-15 holes in there also if you can afford a bag of perlite do 50/50 mix with the compost it will give you better aireation for the roots plus better drainage,if the plant does not improve after a couple of weeks then it is probably stunted it will regain growth but you will have to be paitent,if you want to carry on using the soil you got dont water until you see the plant start to wilt when it wilts it is telling you it needs a drink,i am saying its over watered as the little plant on the left is yellowing from the bottom it could also mean that its hungry but looking at your soil an the yellowing i would say deffinatly overwatered
