The important for blueberries is that the soil is ACID...if not, you need to make it acid if you don't want to see your plant die

First one could be understanding or perhaps not enough nitrogen, how often are you watering? The second one does look like it might be the beginnings of iron chlorosis (which is a sign of high pH) so I agree with Francesco that you should make sure the soil is acidic for them, they like low pH of 4 to 5.

The first isn't fertilizer burn. If only a few leaves it's not worth worrying about esp going into winter.

I'd agree on the second, possibly pH issue.

Fruitnut, I had a very similar problem on my blueberry Toro and Cara's Choice. The leaves looked half brown, spread quickly. Both plants died. I have no idea if it is a blight or an environmental problem? The other plants never showed any signs of this happening. I replaced Cara's already and will replace Toro in the spring. I like both plants and want examples especially Toro, which has super sweet berries.

I just measured the PH on both plants. First pic one has a PH roughly of 4.9 and the second pic one of 5.2.

However I am using this PH meter (link below) in 5.1.1 mix, which is a bit basic:

http://www.bunnings.co.nz/mcgregor-s-ph-level-meter-_p00285698

I am watering with normal hose water, with ammonia sulphate about once a month with additional blueberry food in two feedings (it is spring here).

Also on one the bushes today I noticed leaves with red/brown veins and yellow around those veins (pic below):

Try supplementing the Ammonium Sulfate which is just nitrogen. Use Holly-Tone, cottonseed meal, or another acid loving fertilizer. It looks like some deficiency is occurring.

I did apply a blueberry specific fertiliser in two doses, but I am not sure if I added enough. Was unsure, as the stuff was a bit light on info.

Your "normal hose water" is probably alkaline. Change to rainwater if possible. If not acidify the hose water with battery acid which is 33% sulfuric acid.

I also wouldn't trust a $12 soil meter. I once read on one that it had an accuracy of +/- 0.5. Even if it is properly calibrated, pH varies according to moisture level. Most labs use a 2:1 solution. I talked with a soil scientist and he said that pH will vary if the sample is dried first, then wetted to the 2:1 solution. He suggested calibrated the pH meter and adding 2 parts water / 1 part soil without drying first. The better soil meter cost about $75.

OK I have watered with 2 tablespoons of white vinegar in 5 litres and then applied 2 tablespoons of sulphur to each one.

Add to this I had lightly foliar sprayed with some trace elements. Hoepfully that will help them out.

be careful with the ammonia sulfate. It burns easily...and certainly can result in leaves that look like the first pic.

I fertilise at a rate of 1/4 tsp in a gallon for the ammonia sulfate. Maybe I have been applying it too much. Aiming for once a month now. That sound about right?

Once a month just to maintain growth. Once a week to force strong growth. Your mix rate is actually on the low side. You can mix 3-4 times that strong as long as there is significant leaching when applying plain water between fertilizer applications. In other words just be sure the fertilizer doesn't build up in the pot.

Good to know I haven't given it too much then.

One thing I was wondering is that I have given them both blueberry food (not sure I will use it again), but given it roughly the amount as stated as a side dressing (8 tbls) in two doses. Is the side dressing amount roughly right? could this be causing my issues?

8 tbls is a huge amount unless it's organic or weak. Can't say for sure not knowing what you're talking about. Might not know then.

Are these in pots? A picture showing the whole plant would help.

In general more smaller applications can't hurt.

I will try and get a pic. They are in containers in 5.1.1 mix and the application was of granular fert just shy of the amount they stated, so it could be a pretty rubbish fertiliser.

If it was over fertilised will it just flush out in 5.1.1?

The soluable things like nitrogen will leach out. Other elements won't but I doubt that is the issue. I'm not sure you have much of an issue.

Well that is good to hear. I will see if adding sulphur and vinegar to my waterings will change things.