A good key result is measurable and time-bound — "grow subscribers" is vague, "grow to 15,000 subscribers" is a real key result you can score at quarter end.
OKRs are designed to be ambitious stretch targets. If you consistently hit 1.0 on every KR, your targets are too easy. 0.7 average signals you pushed hard and made real progress.
It happens — priorities shift. Note it in your weekly review, redirect that effort to the other 2 KRs, and be honest about it in your quarterly review rather than quietly dropping it.