Without knowing your specific health stats this would be my guess. Poppers cause your blood pressure to drop which can cause headaches. The fact that your finger tips went blue is a sign that it went pretty low. Can't say why it happened this time and not others (possible you had too much too quickly during this session?)
In any event please get your blood pressure checked. If it turns out you have low bp I'd avoid poppers altogether as they could cause your bp to drop to dangerously low levels.
If your bp is fine I'd still consider giving the poppers a break. In my personal experience I've found you can lose sensitivity if you overuse them and will need to huff more to get the same effect. If thats the case with you, a couple weeks break should reset your sensitivity.
Good luck.