Originally Posted by MoneyMitch
i know its from the ammonia.. im talking about inside them.. what in their body causes this
my limited understanding - ammonia irratates tissue especially delicate gill filaments which thicken, clump together, and can even hemorrhage (hyperplasia). This reduces the fish's ability to absorb oxygen. It also limits the fish's ability to expel ammonia; the natural biproduct of digesting proteins. Consequently, internal tissues are effected and would guess this might cause the red streaks. Maybe dont feed for a bit, especially high protein feed.
what is the pH? i know it's borderline anethema to the prevailing opinions on this site but might suggest to attempt to slowly lower the pH to further reduce the toxic NH3. Lowering temperature can also help but to a lesser degree.