No, I use Miracle Gro acid fertilizer which is just urea. I use it when pH is good. It doesn’t really change pH much compared to ammonium. If your soil is good (and it is) urea is fine.
@alan may know as he uses urea and may know dose for blueberries. What do you think Alan?
OK, just sitting there like that? Probably establishing roots. The cold can cause redness too… They should benefit from being fed.