first picture shows a nutrient deficiency. next picture show old leave being discarded. last shows young leaves yet to turn dark green with some deficiency. Add a table spoon of both sugar and vinegar to your water/feed solution to start with. I use Miracle Gro or Miracid. Both being 24-8-16 or in that 3-1-2 ratio.

Looks like it could be Citrus Thrips damage. The new leaves look good, could be the soap got them. Keep an eye out though, as there are several generations each year. Damage is pretty minimal on mature trees, but as you've done, they should be controlled on young trees that don't have the leaf volume that an mature tree does.

If they come back, Spinosad is more effective than Hort soap on them. It is also organic, and is not damaging to beneficial insects that can prey on the thrips.

To make the Spinosad more effective, add some Horticultural oil or Neem oil to the mix. It helps it spread and stick. Mix both in warm water to help it mix thoroughly.

Here's an interesting article on them;

http://ucanr.edu/sites/KACCitrusEntomology/files/141916.pdf

And Steve has good advice also, it does need more or better food.