Did you test the Ph of your soil? That could solve
all your problems?

I won't worry. Red leaves are common in cold and wet spring weather. The plant should green up in a month or so.

I would not interpret red leaves on a blueberry shrub, in the spring, as a defect or problem that needed to be corrected. It is normal for the leaves to be mostly red when they first emerge, and sometimes they are varying shades of red and brown. As long as the leaf appears to be hydrated, it is very likely healthy. The chloroplasts need more time to develop, and when they do, the leaf will turn green. This process should be completed by mid-June. I like to feed our blueberry shrubs fertilizer, dissolved in tap water, in the spring. That is when the shrub is leafing out, flowering, and developing fruit. Typically I will apply fertilizer once a month in March, April, May, and June. Sometimes the ground is still frozen in March, so the process gets pushed back a bit.

I agree that redness is normal in the spring, but redness is also a sign of stress. They may be too wet, so try to dry them out. It's not that serious. Nitrate fertilizer is not great for them, but one dose should not hurt them. With time they should be OK. Keep us updated.
I myself had a hard time adjusting new plants to the sun and turned mine a good red too. They look great now, but it took a month.

Agree with all above.......my container blueberry leaves won't look normal 'til at least a month from now.

Thanks.