No, the liquid feed won't do anything. You need to do some serious pruning to rejuvenate fruit production. Blueberries fruit on last years growth. After 4 years, blueberry production declines. Remove 20% of the oldest, diseased & damaged canes. This will control diseases & pathogens, open up the bushes to more sunlight & promote newer & more productive growth. Prune out the oldest canes annually. The best time to prune very early spring.

I assume you mean fruiting next year not a re-fruiting this year. and do you mean blueberry Vaccinium is the botanical name.

Paul do you call blackcurrants blueberries? some times common names are confusing. Its just that Blueberries Vaccinuim are a small shrub and don't produce 'canes'
in the old days I only knew them as Bilberries.

Blackcurrants are a plant with the name Ribes. Blueberries are Vaccinum
assuming you mean Vaccinium are you growing them in ericaceous compost?
the website below gives lots of very good advice.

https://www.rhs.org.uk/advice/grow-your-own/fruit/blueberries

hope this helps.

welcome to GoY too :o)

Blueberrries will begin to fruit on last years growth. The growth will increase in production for about 3 years then begin to decline. That's when you cut it to the ground making way for new more productive growth. Never cut the whole bush all at once, just 20%.