Check the soil. Likely it's too dry. Blueberry roots are quite shallow. They need to be mulched to retain what moisture they receive for a while. If they're already mulched, the half inch of rain might not have made it through to the roots.

A picture of the whole plant would be helpful but seeing the leaf alone makes me want to ask this question.

Did you recently fertilize or is there a chance the rain water moved some fertilizer from your lawn/garden/trees over to your Blueberries?

An over fertilization tends to make the leaves dark green. At the same time browning occurs on the leaf tips and leaf edges and works its way to the center of the leaf which is why I ask.

BBerries require very acidic well drained soil. All the rain may have caused roots to die. I grow mine on a ~12 inch tall mound just to get drainage. My uncle grew large amounts on a sloping bank. If the roots sit in standing water or very wet soil very long the roots become anoxic and die. Actually that's a good rule for anything other than willows and rice, but some plants are more sensitive than others.

Tho' mulch may be desirable, dryness didn't cause that sort of leaf damage 3 days after a 1/2" rain.

Have you done anything recently to acidify the soil ? BBerries require acidic soil to function - tho' many sources suggest ammonium sulfate (it's in a lot of rhododendron/azalia treatments) adding elemental sulfur to the soil is a much better long term solution. I doubt that suddenly became a problem after 3yrs.

Thanks for all the responses. I think it is too late for these plants. All of the leaves on both plants are now brown with green centers. This happened very quick and was a surprise. I did have mulch on them but I neglected the acidity and moisture. Drainage was not a problem since my land slopes into a creek. When I get the new ones I will surely build up a mound to plant them in and make sure that the soil is acidic enough. Thanks for all the tips.

We have 1,000 BB bushes and have lost 26 so far this year..They were planted last fall and we all doing fine until the heat hit..I have mulched with 4-6 inches of sawdust and the ground underneath is evenly damp even with the hot weather...

I had a Guy from the University Of KY AG dept come down and check them out and no infections had occured from samples taken..No overspray from herbicedes either..He concluded that the 105 degree air temp simply cooked them..I also lost 1 kwansan cherry that was 8 years old and almost lost a 10 year old ash the week the heat hit..

I have seen this before where the heat simply cooks the plants in there own sap..It was weird how it just happened to certain plants and certain trees though.. I'm not too worried as there was nothing I could do to prevent it...We all do the best we can..That's all we can do..I'll just replace them this fall..

So once this happens that's it? no way to save them? I just went out to water and I too had a few light rains the past week and I was just out there a few days ago and picked a bucket of berries from healthy thriving plants. Now I'd say 1/2 of them are burnt up.

Is there absolutely NOTHING that can be done to save them?

I am so bummed.

Mine are potted up and all grouped close together.