needles

Hello all, I have some experience with bonsai, 3-4 years, but no real training. This Black pine was a new addition this winter and recently it's begun having brown tips. I have never had a pine, but from my research they lose their old needles very slowly, but at the same time once they show...

It's Spring here in South America and some needles of my cascade red pine are turning yellow on the tips. New growth (this year's) is blue/green with no yellowing; but old needles have visibly damaged tips. I have searched online, and at other bonsai forums, but apparently could be from "normal"...