Blueberries hate to be dry, red leaves do indicate a problem sometimes. Low acid, or high alkaline. Go for about 4.5 to 5.5 Ph. It's super hard to over water them. Do not let them dry completely. They also like to be fed a lot, but I would not feed it till you see growth. You might have to wait till next year at this point.

Brown leaf tips and lack of growth sounds like the result of the plant not being kept constantly moist.

You didn't post pictures of your plant so take a look at these posts of people complaining about their blueberries having brown leaves to see if it's the same as yours. gardenweb/query/blueberries-brown-leaves

Daren

Paul, at this time of the year mine are turning red too. Did you fertilise it at all when you bought it ? You mentioned that you recently moved it to full sun , did you have it in a shady place before ? As mentioned in the previous posts , blueberry love Being constantly moist so maybe it is a case of too little water lack of nitrogen and not enough sunshine. It will go dormant soon so be ready for next year.