The progress becomes slower as the skill is getting closer to the maximum limit. You can see it here. The skill is at maximum and there is no yellow zone in the gauge.
Mida lähedamal on talent maksimumile, seda aeglasem on selle areng. Te näete seda siin, tema talent on maksimumi peal, mõõdikul ei ole näha vähimatki kollast ala.