The light can't reach the lowers with decent enough light wave radiation due to distances between the light and those flowers at the bottom, in these situations the plant either stretches the branches so they are at a decent level or she uses the energy in portions that are already at a decent level for light reception, so they just don't develop as well, you would want to cut these off early on still in veg or at the very beggining of flower.
You can do it like this if you wish to in future grows:
proceed to cut off 2 of those lower branches that you don't need and wait a couple days, when the place you have cutted these at turns dark nearly black in color, go ahead and cut 2 more above, and do this only a couple times, don't over do it if you don't want to stop your plant's progress, they will be stressed regardless as you cut em off but if you are too agressive and do bad cuts then she will stagnate and stop growing for 2/3 days while recovering, during this time its as if she wasn't growing bud at all.
Safe option-
Don't cut them, you are so late into flowering that its not worth the risk, by this time is when they get denser and grow the most, its best if you don't touch the stems and instead just let her redirect energy as needed, as you can see she is not growing as much the bottom branches, because the plant knows those are not as close to the light and would need some massive vertical growing and then she couldn't support the weight, so she would need to thicken the branches as well wich means more energy, so the plant just spends the energy with the top buds wich are close to the light. What you would do by removing those lollipops in the end of veg or early flower, she has already done on her own, u remove them so they dont suck power for nothing, but the plant already aint giving them power, so job done. Do nothing m8.
good luck and stay lit growmie, if anything just dm me.