Growing very quickly:

Evaldas,
One word only: Beautiful.

Is it possible that the foliage has stopped growing for some reason in the middle of their normal size?

Evaldas,

I really like your setup. The trees should be lit very well and very efficiently.

I have noticed that leaf size is correlated with light levels. Large leaves are produced when light levels are low and smaller leaves are produced when light levels are high.

I cannot tell what the actual leaf size is from your pictures. I can only see that the new leaves are smaller than the old leaves. Is is possible that the new smaller leaves are normal sized leaves and the old larger leaves are abnormal because of low light levels when they grew?

How many hours per day are the lights on?

The lights are on from 7 a.m. to 10 p.m. So that's 15 hours.
Maybe the leaves stopped growing because I watered them with micronutrient fertilizer (no NPK). I usually fertilize on every watering, so maybe the plant didn't react well to not getting NPK that one time.
The older leaves (from the nursery) are normal sized, the new ones are almost half smaller.
I mist it every evening after I turn off the lights with distilled water. By the way someone who said here that my tree wouldn't be doing good with the "mini green house" standing next to a radiator was wrong.

Don't worry about it Evaldas, its normal, some of the leaves will grow to be smaller some will be larger. Pretty much all types of citrus develop leaves that are different sizes. Since you are not using CHC or equivalent soiless medium, the fact that you did not use a NPK fertilizer one watering will absolutely not effect the plant in mid growth. This is because the NPK fertilizer will remain in the soil even after you water with micro nutrient water, it will flush some out but not all, keeping the tree nourished until the next application of NPK. Unless you are flushing the soil with several gallons of micro nutrient water you should be fine and even if you did flush out too much the problems would be different, they would show up as deficiencies, like a nitrogen deficiency, which your trees are not exhibiting in the photos.


Keep doing what you are doing, don't over think the process. If the tree is growing and looks healthy then it most likely is.