Utah County Utah blackberries
I'm not prepared to give you a conclusive answer to your problem.
It appears that you have a variety problem for your climate and soils. This problem would be best directed to your state extension system in Utah, who has more familiarity with blackberry performance in your area.
This type of problem may result from plants being infected with viruses, insufficient water prior to- and during bloom period, excessive heat during bloom and soil nutrition problem. Some of your foliage appears to show interveinal yellowing (chlorosis) and marginal burning, which may indicate high pH soils and iron deficiency, excessive salts, or other soil problem. Having your soil nutrient levels and pH and your irrigation water tested for salt presence may be helpful.
Again, this question should be posed to your county or state extension horticulturists who you will want to describe the variety that you are growing and how it may be expected to perform compared to other varieties recommended for your area in Utah.