Photo 1 shows an 8+ petaled flower, which is a bit unusual for the species. The other photos show a nearby plant, with 6 (I think petals). Many individuals here have >5 petals.
Petals are usually light pink, sometimes white, in these populations of buttercups, and always fade from whitish towards pinkish with age. The flowers in the last photo, though, didn’t look too young too me, and so, I think white color may persist with age in some individuals.
Locally common, in mid flower on north aspects, late flower / past flower on northwest aspects. The flowers shown here were on a north aspect, below a ridgeline, growing in moist soil.