Any ideas to ramp up bud density?
First of all, you have beautiful plants, you should be proud.
Regarding the thin buds, I'm jumping to a conclusion based on 50% of your photos being in the shade. That suggests your plants are in a shady spot, they will do better in full sun. I see internodes a half inch apart that might be 1/10th of an inch if they were in full sun. The shorter your internodes are the denser the buds are. Some plants lean toward longer nodes, so it could be genetics, but I don't think that is it.
So I'm an indoor grower, because of the law and stuff... But when I started growing 40 eons ago, the most important lesson I learned was how light and heat affect my plants. You are outdoors, so lets skip past the temperature considerations. Low light
may be causing your internodal distance to be too long, this means the stems are growing to gain height to try and reach the direct sun, which puts distance between the bud nodes making them appear thinner. The good news is excess internodal growth doesn't hurt your yield much, but the buds will appear less dense and the plants will grow taller. Where it may hurt you is energy put into growing stem takes away from bud growth and
IF this is your actual problem it also means your plant will be smaller and thinner for lack of sun. But low light also slows the plant growth down, so a 10 week plant might want 15 weeks to finish... so you may get near full weight yield, but over a longer period of time... I suggested 50% more time, but that is a guess. When I had this problem it was much worse because I was indoors.
You are outdoors, but in your photos I see mostly shaded images, and one with a sunlit field in the background but your plants sitting in the shade. If you must plant by a house, plant on the south wall. It may be a photo early in the morning, or later in the evening, so I could be wrong... But your plants should be in the direct sun for the majority of the time the sun is up. Blue sky and shade will not grow anything but stem, buds only grow well in direct sun. The farther north you are, the more important it is to not waste time with the plants in the shade. The difference between shade and full sun is a lot more than your eyes perceive, because your eyes adjust. The shade is around 10% as strong as the sun, and it is below the threshold for what is needed, so it almost doesn't contribute to plant growth (except for robbing plant strength by growing stem). In the shade your plant wants to grow stem and not much more, in the sun it grows leaf and buds, and only enough stem to spread out in the sun..
I also grew food crops over the years, and shade areas are only good if you are trying to survive 112ºf with tender plants, so you protect them with reduced sun when the heat of the day is setting in trying to kill everything. But that is survival, not growth. To actually grow you need the direct sun all day, not just part of the day.
I use light meters to get my indoor light up to and even past the level of direct sun, and my autos see 24 hours a day of that direct+ sun. The plants are dense, you cannot see through any plants, they have short internodes, and very thick growth. Occupying the same volume of space, I wager my plants weigh 20 times more than yours do. They are small plants in general because they are autos, but in terms of plant mass my 2' tall plants are out producing my expectations.
If you wait for the shade to take pictures, and your plants see 13 or more hours of bright direct sun, then pay me no mind. BUT if your plants are under blue sky shade for 6 hours a day, they are being starved of their source of energy, and need more sun. In general most crops want flat earth, no trees or buildings, just sun up to sun down direct sun. You
can give them less sun successfully, but you pay the price with long internodes.
It boils down to simple chemistry. Sunlight plus water and carbon dioxide produce ATP, which is the universal cellular source of energy. The more ATP you produce, the more energy to grow you have. The ATP is used to build every other molecule in your plant. The more ATP you have on hand, the less strain growth (stem) and the more vegetative growth (leaf/buds) you will see. Pot can consume more sun than the sun can provide, and it can consume more nutrients, more water, more co2 (and more oxygen, plants breath oxygen to consume and utilize the ATP, co2 is fuel for making ATP)