Any chance water or fertilizer is splashing on the leaves?

Blueberries like damp fast draining soil. Your soil mix looks peat based which holds a lot of water and looks damp but is not fast draining.

If it were mine I would plant it in a a better soil mix with some peletized Ironite along with that sulfer.

Here is the soil mix I use for my six plants that are all fat and happy.

MY BLUEBERRY SOIL MIX

1 Part Perilite.
1 Part Potting Soil.
2 Parts Small Pathway Pine Bark.
2 Parts Sphagnum Peat Moss.
1 Tablespoon Cotton Meal per gallon.
1 Teaspoon Granulated Garden Sulfur per gallon. Could be more if the pot is small but mine are in 15 gallon pots..
1 Tablespoon Granulated Ironite per gallon.
1 Tablespoon Down To Earth All Natural Fertilizers 4-3-6 Acid Mix per gallon.

After they start leafing out I fertilize every 2-3 weeks with Miracid For Acid Loving Plants at about 50% of the recommended dose. I give them a small drink of water just before and just after I fertilize so I donÂt shock the roots. Not sure how necessary that is but thatÂs what I do and it works for me.

If the leaves start to turn red-ish I water them with a mixture of 1 Tablespoon white vinegar to one gallon of water and that usually does the trick.

To stay on the safe side stay away from fertilizers with nitrates and donÂt add any calcium or lime to your soil mix.

I plan on adding a small hand full of Granulated Garden Sulfur and Cotton Meal under the mulch each dormant season to maintain the PH.

The plants are nice and healthy growing well and producing fruit so I guess they must be happy.

Thanks very much! I don't think water or fertilizer splashed on the leaves recently. . . but the last few days when it started have been VERY hot all of a sudden for the last 3 days and it's on a south facing deck. Do you think it could be too much sun? I moved it to a side of the deck that gets a few hours less sun (still south facing though). I had that problem with hot peppers last year.

I just use pro-mix and added extra perlite to help w/drainage. I also have marble chips on the bottom to help w/drainage (which I later learned was a bad idea for the pH).

I've used vinegar to get past a period where I thought the pH was too high b/c the leaves turned red - and it worked. I ordered a tester so hopefully I won't have to guess. I didn't think it was low acidity b/c I didn't think that would cause the drying out - do you think that could still be low acidity?

I am in the city and don't have easy access to a full garden center but I'll try to get out and get that mix next weekend if it hasn't turned around. Thanks very much for the info!