Getting a lot of black/very dark brown pollen coming in. Any ideas?
Himalayan Balsam does leave a stripe but it's creamy white when I've seen it. Very noticeable too - all the way down the thorax. Orange/yellow pollen on the head may well be from Common Toadflax (Linaria vulgaris).
If it's a little yellow dot on their foreheads likely to be OSR.