How old are they? New young plants from garden centers may not bloom for some years after planting, even though they were full of flowers at time of purchase. The reason for this is differences in conditions between final planting sites and commercial production environments.

When were they planted, where are you located and what is your USDA Zone? It also sounds like they may be potted... if you are thinking of leaching due to overwatering? Are they or are they planted in the ground?

Luis and Embothrium,

They are all well established bushes (25+ years) and have done well in the past. We are in zone 9. One of the bushes is close to the house and the other two are in a bed along the driveway.

Hard to tell. You need to monitor the trees more closely.

Start by monitoring if they are producing flower buds. That should start soon, if it has not already (leaf buds look like flower buds so, yes, you may need to wait for the flower buds to get a tad bigger). Then monitor the flower buds as they grow, get larger and open. Once "something happens", you need to investigate it further.

Lack of water can kill the buds and you would notice when flower buds brown out but you have to be monitoring and keeping track of temps to see this. Being 25 years old, they probably need more water than a few years ago for example...

I would also do a soil test to see if there are any mineral deficiencies or too much minerals (too much nitrogen, for example). Observe the location and nearby non-camellia trees; see if the other trees around the camellias have grown and the camellia trees are now in too much shade.

I would make sure they are well mulched and the decomposing mulch adds/replaces spent nutrients to the soil.

I would also take lots of pictures from various angles and close ups to try to see when the problem happens.

Finally, be on the lookout for pests like camellia bud mites: https://www.gardeningknowhow.com/ornamental/flowers/camellia/treating-mites-on-camellias.htm

Thank you Luis. I will monitor them more closely using your suggestions.