First: Are all the same variety?
Different varieties bloom at different times during the season, usually late Nov until May in my area.
Very cold temperatures, as we experienced in early Jan, can cause the buds to remain closed.
Camellias sometimes have a mind of their own and bloom at different times during some years.
I have one C. japonica 'Debutante' that has bloomed early, Dec-Jan, then rested for a month or so, then began blooming again in late season.
Here's a few of the more than 3,000 named cultivars of Camellias and their usual bloom times"
'Betty Sheffield Supreme' - Late; large; red.
'Berenice Boddy' - Midseason; medium; light pink.
'Daikagura' - Early-late; large; rose-red.
'Debutante' - Early-midseason; medium-large, pink.
'Desire' - Midseason; medium large; pale pink.
'Kramer's Supreme' - Midseason; very large; red.
'Kumasaka' - Midseason-late; medium-large; pink.
'Lady Clare' - Midseason-late; large; dark pink; above-average cold hardiness.
'Magnoliaeflora' - Midseason; medium; pale-pink.
'Mathotiana' - Midseason-late; very large; crimson.
'Guilio Nuccio' - Midseason; very large; rose.
'Nuccio's Gem' - Midseason; medium-large, white.
'Pink Perfection' - Early; large; pink.
'R.L. Wheeler' - Late; large; red.
'C.M. Hovey' - Late; large; red.
'La Peppermint' - Late; medium; white w/pink center stripe.
'Jury's Yellow' - Late; medium; creamy white to pale yellow.
'Morning Glow' - Midseason; medium; pure white.
'Prof. Charles S. Sargent' - Early to late; medium; red.
'Governor Mouton' - Midseason; medium; red w/white splotches.

I grow most of the cultivars listed above, plus many others. The only ones that have bloomed so far, are 'Debutante' & 'Prof. Charles S. Sargent' and the early Jan. freeze killed all of the blooms. They are just beginning to resume blooming, after the recent warmer temperatures. All of the others still have tight buds, but with a hint of color.

Some years there is a magnificent show of flowers, other years, there are a series of color, then brown, mushy globs! Just be patient, the later the buds decide to open, there's more of a chance to enjoy them!