Some of this leaf damage is likely due to winterburn, which many evergreens experience depending on winter weather conditions any given year. We've seen widespread instances of winterburn this season, in part because of the drastic temperature fluctuations earlier in winter. Camellias are one group of evergreens we tend to see winterburn on more regularly, perhaps because as a group they are less cold-hardy than other evergreens. (Though local nurseries do tend to stock only those varieties that are more reliable in our winters.)

Nothing can be done to reverse the damage of winterburn, but plants with healthy stems and roots can replace foliage once they resume growth in spring. Siting plants out of the brunt of winter winds can help avoid this in future years; for example, the wind protection of a house wall or solid fence can help. Camellias also prefer part shade (even in winter), so a lot of sun exposure while the canopy trees are bare can cause the leaves to get a bit "tanned" as they bronze due to stress. This too can resolve itself if the plants receive more shade once the trees overhead leaf out. If it's still receiving lots of summer sun where they're growing, we recommend moving the plants to a part-sun/part-shade location where they get a bit of a break from the hot sun in summer.

Camellias are sensitive to over-watering and soils that don't drain well, so make sure a nearby roof downspout outlet or other source of drained water doesn't saturate their root zone. During the growing season, as with any young plant still establishing, they should be regularly monitored for watering needs by feeling the soil around six inches deep near the roots. If becoming somewhat dry to the touch at that depth, they can be watered well. Drought-stressed evergreens can be more prone to winter dieback or leaf injury. Mulching over the root zone also helps retain moisture and insulate from temperature extremes, and while we see a little bit of mulch around one of the plants, it isn't providing much protection from lawn care injuries (exposure to any weed killers used or mowing or weed-whacking stem damage, for example), so we suggest expanding this mulched zone to around a foot around the main stem(s). Keep the mulch only about two inches deep and don't pile it against the base of the Camellia stems so they continue to get good airflow.

Do deer visit the yard? (It might be only overnight.) If so, they are known to eat Camellia buds and foliage. You do mention leaves shedding earlier, and that could be a response to soil moisture stress (too much or too little can both cause leaf loss), assuming the leaves were seen on the ground under the plant. If they simply went missing, then deer might be to blame.

Peonies and vegetables aren't at higher risk for problems even if the Camellia has a leaf infection. That said, the conditions that allowed the Camellia to become infected might also promote disease among other plants, even if the pathogen itself isn't spreading from one plant to another directly. Often, leaf-infecting fungi and bacteria are more successful at causing disease when the plant's foliage remains wet for long periods, such as from irrigation or rain/dew that doesn't dry quickly due to shade or poor air circulation around the plants. (Avoiding plant crowding, such as from densely-planted vegetables, can help reduce this risk.) Similarly, soil that stays too wet for too long due to compaction, poor drainage, or over-watering can also result in other plants developing root rot, even if the rot disease isn't directly moving from one infected plant to the next. If the vegetables are being grown in raised beds, this is less likely since those beds tend to have better drainage than ground-level plantings.

For now, just monitor the Camellias for signs of new growth as we move into April and May, and if any stem tips remain bare as other leaves are expanding, you can trim them off as they've probably died back. No fertilizer is needed, and if the lawn that surrounds them is being fertilized once or twice a year, that's plenty of nourishment for them. If you think they need moving to a somewhat more shady location for summer, now or April is a fine time to move them; retain as many roots as you can when digging, which should be fairly simple as they're young still and probably don't have very extensive root systems yet.

Miri