Looks like overwatering. How often are you watering? Overwatering will cause deficiencies, toxicities, pH problems (gets very acidic), AND can cause root rot.
Those smaller the plants, the longer it will take to solve an over watering issue. This is because you don't have a large root mass to absorb all of the water too quickly. These will stay stunted for quite a bit until the issue gets fixed. Just lay off the watering for a bit and go easy and they should recover within a few weeks. Underwatering is easy enough to fix, but overwatering will cause a plethora of problems.
Some people may even recommend starting over, as it's going to take at least a couple of weeks for them to recover.
Sorry to be the bearer of bad news. It is fixable, but will take a while and starting over may be easier.