I'm not an expert but I do grow blueberries. First, I don't let them have the sun directly on them. They don't like it. Dappled shade is best as their leaves can be scorched. I have grown them in pots until this year and as they survived our harsh winter without protection I decided to put them in the ground. They like a slightly acid soil and they like moisture. Their roots are quite near the surface so once planted and well watered they should be mulched. I use pine needles and shredded pine bark.
I never water with tap water. They don't like the lime content. When our water butts get dry - which they do - I don't water them at all.
As soon as they have finished flowering I cover them with fleece so that the birds don't pick off the developing fruits. I keep them covered until the last fruit is picked.
I don't prune them until they are in their third year and then I prune out the old wood but make sure there are at least four to five good strong stems for the following year.
If your bought plants are not doing anything then there's a problem which may be solved by following the above advice. You said you planted them in the right compost - what was that? I just use ordinary garden soil with some mulched pine needles incorporated.
Hope this helps.