The "dark green spots" are the color the leaf should be; the lighter portions are likely a deficiency of some sort; not to worry if your new growth is fine. What you are seeing is how the tree WAS; the new growth is how it IS.

I agree. Leaves look good to me.

Thanks for the input John and Vladimir! The last picture of my mandarin leaves, you think that is a deficiency as well? I just want to make sure I'm headed in the right direction.

It looks to me that the large pale leaves are the older leaves, in which case it appears that the tree had a nutrient deficiency in the past. It will probably drop those leaves soon. From now on, make sure that you are feeding it well with Foliage Pro 9-3-6, 1 Tb/gal every time you water while it is actively growing. Make sure it needs watering by digging into the soil an inch or two with your fingers to see if it feels moist.

Thanks for the information Vladimir! I am fertilizing regularly, with Miracid for now. I am going to buy Foliage pro soon. I want to repot my citrus in the 5-1-1 mix. I just finished reading about it and I will slowly make a batch.

I had leaves like in the first picture on my lemon, when I sprayed with mixture of oil and soap and I think the oil ratio was higher. I heavily sprayed the tree and the leaves looked like that for about a week or so and then it went back to normal colour.

That would make sense, since I sprayed horticultural oil on my citrus to control some pests.