I don't see any symptoms of a salt build up in your container. A salt build up shows a burring of the leaf's tip and along the leaf sides. In Canadian Citrus's first picture I'm not sure what going on . The second picture is showing several leaves with a manganese deficiency. Some might think it is a magnesium deficiency because of the darker green delta shape, but it can't be because magnesium deficiencies show up on a tree's older leaves. To correct a manganese deficiency you can apply manganese sulfate either as a foliar spray, or to the soil, OR you can simply do nothing. New ctrus leaves very commonly show a manganese deficiency, almost always they grow out of it as the leave matures. During the winter months water your tree with a lukewarm water (70 - 80-F) solution. This will help the health of the root system, and fertilizers to reach your tree more efficiently.