Old hot sauce making me sick?

Am I crazy for thinking that the smaller bottles of hot sauce seem to spoil when there's less than a quarter left in the bottle?

I love making egg burritos in the morning with hot sauce, so far I've experienced this with regular valentina and tapatio, it's like the less sauce there is the faster is starts to ferment. It starts to smell and taste a little different, and it oxidizes to a slightly deeper color. Stomach is not a fan.