First off, that soil doesnt look very good bro. I add 60% potting soil mix, 15% perlite, 15% coco coir, and 10% worm castings. Gotta spend time and $ on quality soil or it's pointless. Onto your plants.. obviously they have some sort of defeciency. Either low O2 to roots, Nitrogen (unlikely), or Magnesium/Calcium (probably). Need to start them on a feeding program with a micro nutrient. Superthrive is good as well and cheap.