Fatness is difficult to determine without assessing with your hands too. Some animals may appear too fat, but when you palpate them you can feel bony prominences (and it's only due to lack of work and poor muscle tone that they appear fat) and others may seem too lean but they're fit and...
Guttural pouch mycosis?
Firstly, is it the same nostril that bleeds each time, or does the blood come from both? If same side each time, it is more than likely an upper respiratory issue. If both, then a lower resp tract problem would be higher up on the list.
The only way really to...