How large were the plants when you planted them ? Were they very young small plants ?
If you'd bought plants that were about 16" high they're going to take a few years to reach 4-5 feet, if you'd planted plants that were very small it'll clearly take a year or two more and no amount of extra feeding will speed this up.

How long have the plants been in the ground now ?
If it's been more than a few days i wouldn't disturb them again, leave them where they are.
If the soil they were planted in was good quality their roots will make their way into 'that' and once they're established the roots will cope with most soils, Escallonias are strong shrubs (i too have an escallonia hedge).
What i 'do' suggest is applying a top covering (mulch) of organic material (manure, composted manure) and i'd do this in the late autumn, could do it again in the spring too - this will also protect the roots and the nutrients from it will provide a bit of 'oomph' to them too.

We have escallonias that were planted almost 20 years ago in very rocky poor soil (basically the rock tip from an old mine) and they've grown fine - we're trying to keep them within limits! Small plants settle into difficult situations better than bigger ones as they've got less growth to sustain while the roots are finding their way into whatever soil there is.
Don't worry, don't dig the plants up, just keep them well watered during dry spells for the first year or two - they'll be shoulder high in a few years.

I planted some 5'x5' plants as a hedge and they would surprise you with the ease in which they settled in.
The soil wasn't great at all, much like Beatties poor soil but still these established plants settled.
I 'do' believe that a lot of gardening is down to luck sometimes ..... it 'has' to be because i've done some awful 'shortcuts' before now and the plant's flourished ;-)

Escallonia is one of the easiest plants to grow. I have three in the garden growing as shrubs not as a hedge. My problem is keeping them to a manageable height. I planted them as you have done and they were 5' by the end of the first season. I would not let the stems get too long if you want it to be a hedge. keep trimming back to about 4" and that will keep the hedge nice and tight. That will also allow the plant to put strength in to growing up instead of out. When it reaches the height you want to achieve just cut along the top and then be ready to cut as and when needed. Your planting holes will allow your plants to establish themselves well so that by the time the roots are going out past the compost they are strong enough to cope with it. I feed mine bone meal in the autumn and put a mulch of compost or wood chip down on top of newspaper. Stops the weeds and keeps the moisture where you want it. Many give a boost of fish blood and bone in the spring . Let us know how it goes. Make sure it is kept watered the first year. Welcome to GOY

Many thanks for the advice. (I do not have green fingers – everything I buy tends to die – my wife recommends I search for plants with life insurance!!).

Escallonia was a good choice then! :-)