The plants look like two different species of pine (and dwarf varieties of each, given their stature/shape), probably Eastern White Pine for the first two photos, and the other might be a Mugo Pine (it's hard to tell since we can't see the quantity of needles in each bundle clearly enough).

The Eastern White Pine is exhibiting needle loss for what appears to be two reasons -- one normal, the other a potential indication of root stress or dieback. Although evergreen, pines do normally shed their oldest needles in autumn, and the yellowing and shedding can be fairly noticeable in this particular species, which is natural. Branches whose needles are yellowing/browning all the way to the branch tip, though, are dying instead, and this is what may be related to root health. Symptoms this generalized can be hard to diagnose (it might be a branch infection, for example, and not root-related), but there is no direct way to intervene for either situation since use of a fungicide will not cure the plant. Evergreens like pine can take a surprising amount of time to develop foliage symptoms of a problem, so it's hard to determine when exactly the issue began.

All you can do for now is to trim off any branches that do not have live green foliage at its end. As for the causes of root stress or die-off, we generally look to the soil conditions as a common reason. Eastern White Pine doesn't want to get too dry, nor does it fare well in soils that get too wet or which drain poorly. We see a stone mulch around its planting bed...is there landscape fabric underneath to keep the stone from settling into the soil? (Usually that's how stone mulches are used.) If so, the fabric might be affecting root health by impeding how readily the soil absorbs moisture (and evaporates surplus moisture) and may also be reducing the oxygen levels in the soil, which are vital for root health. We noticed a roof downspout behind the pine as well; does this empty near (or in the direct of) the plant, or is it buried and empties elsewhere? If it deposits rainwater around the pine's root zone, in times of very wet weather, this could saturate the roots beyond the tolerance of the plant, causing their dieback.

Pines cannot replace growth on stems that have become bare (nor will they grow new branches on portions of trunk that are older and currently branchless/leafless). However, the plant doesn't seem to be a lost cause yet. Our weather has been drier than normal all year, and currently we are back in drought status for a large portion of the state. If you haven't been already, monitor the plants for watering needs (both pines) and make sure they don't stay too dry for too long. Feel the soil about six inches deep in the root zone (another reason landscape fabric is not helpful) and water well if/when it's becoming fairly dry to the touch at that depth. Drought stress, aside from causing its own damage, can predispose plants to attack by other ailments, such as opportunistic wood-boring insects and fungal pathogens, neither of which are treatable once set in.

The white residue on the buds of the Mugo Pine is normal and is just resin or dried sap produced by the tree. It does not need removal and can be ignored. Excessive sap flows from bark, like on a trunk, can be a warning sign for pines in some circumstances, but in this case its covering of the buds is not concerning.

We can't see browning branches on that second pine, but if it is a Mugo, it might be due to Diplodia Tip Blight, a fungal disease that certain pine species are more susceptible to than others. No cure exists, and while certain fungicide treatments sometimes help prevent infection from spreading to new growth, they don't always work and usually are impractical to try or rely on. (They have to be applied at least once every year.) If not an infection, browning at branch tips could be related to the same issues as for the Eastern White Pine (too much or too little moisture around the roots) or natural shedding (if confined to only some older, inner/lower needles.

Miri

Thank you for sharing - the pine looks good! You may already be doing this, but if not, monitor it regularly for watering needs given our ongoing drought, since drought stress can result in secondary issues like fungal infection or dieback after a drought has abated.

Miri