Birches do require lots of water and with a limited root system as a new transplant,birch trees planted last fall one would expect to see some winter dieback, small branches, tip dieback, etc. your trees are far from established, so continue to water a lot this season and perhaps into next.
Blueberries certainly require an acid soil, well below a pH of 7.0 (neutral), 4.8 - 5.2. Lots of organic matter besides peat moss should be added into the soil profile. Blueberries enjoy high organic matter soiis retaining soil moisture and lots of airspace. A generous sized planting hole or a raised bed is often done. Winter hardiness will play a large role in survival ability. If the tops have died back and the roots are good, new sprouts will emerge. If you do not see good progress by mid-june, consider replanting.
pH meters and test kits using reagents are available at a high quality garden center. Most of the probes rely on soil moisture so the same soil dry may read different than when moist and a reading in the upper profile will be different that when the probe is pushed in several inches. Be consistant in your testing. Take several readings and average the results, using either method.