Thank you very much fireduck!

I also found the following from an ebay product description for 30 lbs of ferrous sulfate:

This product is used to correct iron chlorosis in plants
Reduce alkalinity in soil and as a mineral feed suppliment for livestock
We use this product in bulk for a variety of agricultural uses.
As a soil applied fertilizer or nutrient: Dissolve 2-4 dry ounces in 1 gallon of water. Coverage is 1000 - 5000 sq. ft.
As a folier application: dissolve 1 dry ounce in 1 gallon of water.

Hmmmmm... Still not sure how often to apply.

Hello there,
Since your plant is potted wouldn't you consider buying some ericaceous compost and repotting it , normally the PH of such a compost is 5 ?
I use FS on the blueberry in the raised bed and I would normally use a fistfull around the plants when rain is forecasted, mind you it rains a lot here.
For my potted plants I used ericaceous compost for the last 3 years , and am about to repot them in the next few days usind the mixing media recomended on the David Willson web site.
You should also water your plants with rain water as the tap could be to alkaline and would make your soil PH increase.
Hope that helps.

The Bountiful Blue's new leaves do have that reddish tinge and then slowly turn a deeper green.Hopefully your plants roots did not experience too much root kill and the plant will bounce back.
If Sulfuric acid is not desirable to use,maybe try vinegar to bring the pH down. Brady

I always use sulfur to acidify the soil for my blueberries. You can get it at 30% or if your lucky you can find it at 90%. My soil is normally 6.5 PH. I add 1/4 cup of 90% sulfur around each plant and in a few months it is 4.3 PH.

Hans

Thank you all!

@Sal73-Ireland I hope not to further disturb the plant by repotting now, but definitely an option for the future!

@Bradybb WA-Zone8 It's well alive, but still :'( OK I will keep diluted vinegar in mind.

@Hans P. Gruetzenbach I have the ferrous sulfate powder on hand specifically for this blueberry plant, reportedly it acts faster than sulfur. I'll try the 2 oz per gallon water recipe above... Maybe twice a year???

It is possible to check the soil pH for a potted shrub, using either a pH meter or indicator dye(bromocresol green). One simply waters the shrub with distilled water, and collects a small sample from the hole in the bottom of the pot. The sample is tested, and the result can be written down on the calendar. The shrub can be checked every three months, until you are confident that the pH is where you want it to be.

I am growing 4 varieties of southern highbush in the San Francisco bay area. I find that the leaves of most of them turn somewhat reddish as they age and especially toward the end of winter. For that reason I would not be too concerned about the reddish tint if the new spring growth is bright green.

These cultivars were planted in half wine barrels in a medium of 100% peat moss with agricultural sulfur and a bit of fertilizer thrown in. In their third year now, they are quite large and producing very well. I have only given water, wood chip mulch topping and a small amount of 10-10-10 each year.

Based on my experience I will do it all the same again when I layer these plants this year..

My biggest problem is the blue jays.

The OP said ph tested above 7 if so, yes they need acidifying else the plant will die. Dirtydan growing in 100% peat moss and sulfur is super acidic and I can see why you have no problems. Leaves most definitely turn red with high ph, and cold, so you have to determine which it is. Some tinge is OK, but they should turn a dark green. I would use the vinegar, which is like a bandaid, the plant needs sulfur. ferrous sulfate is ok but takes about 6 months to work. Add a couple tbsps and wait 6 months. In the meantime use vinegar ASAP! Never just add tap water. Do not put straight vinegar on plant, mix with tap water. Hard to ay how much I don't know what your water is like? You have to test it. You want the water to be between 4.0-5.5.

Thank you everyone. Mysteriously, the blueberry is all happy now with all green leaves, before I did anything. I'll still do vinegar ASAP!!