What is wrong with my blueberries?

[StormySky]

I bought two 3-year-old O'neal plants 4-5 weeks ago and they were repotted into larger containers using a soil mix recipe I found online, comprised of 1/3 peat moss (initial PH ~3.9), 1/3 native soil with compost and 1/3 shredded pine bark with perlite, so the PH of the mix should be low enough. I used the same soil mix on two other 2-year-old blueberry plants (Biloxy and Star) that I repotted at the same time and they are doing fine.
I have not fertilized yet since as I was planning to do that 3-4 weeks after repotting, but that was put on hold when the tips of the leaves started turning brown and dying. The plants have also almost stopped producing new leaves.
They are mulched with 1-2 inches of pine bark and I was checking 1-2 inches deep before watering once a week with rain water.
Both O'neal plants had many flowers when I got them and I did not immediately remove them though I did that yesterday to allow the plants to conserve strength.
Any tips on how I can turn this around?

 

[StormySky]

I forgot to add that I live in Greece and this year we had an exceptionally hot March and April (temp steadily 4-5°C above normal and close to 25-30°C for the last month) so I made sure I keep the soil moist.

 

[YumYum]

Could be a potassium deficiency or some other nutrient. The pH looks fine by the color of the leaves which it also looks like the plant has had plenty of nitrogen by the dark green color which is kind of puzzling. It could be transplant shock and/or the soil mixture doesn't have enough nutrients. It could use a good fertilization of every thing but nitrogen but it has to have a low pH. Also don't use any nitrate form of nitrogen on blueberries. Nitrates are toxic to blueberries.

 

[StormySky]

Could be a potassium deficiency or some other nutrient. The pH looks fine by the color of the leaves which it also looks like the plant has had plenty of nitrogen by the dark green color which is kind of puzzling. It could be transplant shock and/or the soil mixture doesn't have enough nutrients. It could use a good fertilization of every thing but nitrogen but it has to have a low pH. Also don't use any nitrate form of nitrogen on blueberries. Nitrates are toxic to blueberries.

Thank you for the quick reply. I will try applying fertilizer and see how they respond.