I use an 11-3-6 fertilizer and use it every 2 weeks.

I think the tree will be fine. I wish you luck.

By now, the flowerleaves are allready slowly diying, making room for the fruits. Still got my fingers crossed :d

The 3rd flower started turning brown even before it was opened fully. Is that normal? :s

I think I gave it to little water because now the new opening flower is as white as snow.
Last year I was reckless with water, now to carefull.

edit: The new flower blew off with a a little blow of my breath...
What the hell is going wrong? I had 4 flowers open and only one remains. I've got a lot of fresh leaves but just this morning I saw 3 of them (about 1 cm in length) just laying on the potsoil. Nothing seems to be really stuck on the plant. And the flowers a swell as the buds fall off even when they look fresh. Those new leaves are perfect graan.
I just can't figure this out!

The plant is inside a tunnelgreenhouse but this remains open during the night. This functions more as a wind/rain shelter.

Has any of you ever had leaves and buds that start do 'die' from where they are attached to the branch? I've got some that look very nice but other that are dying. :s
Took some pictures just 5 minutes ago. The last 2 show the damage starting from the branch.

I suspect there are no mature leaves on your tree or in small number. The citrus trees store the food in the leaves and very small amount in twigs and branches, in the root almost no extra food, different then deciduous fruit trees.
Where the twigs die back it's mean that your tree is using the food from there to can grow the new ones.
The flowers request extra food, I would remove the buds and give more care to the new twigs and leaves.

All the best to you and your trees.

But the twigs aren't dying but the buds and leaves are (some of them e.a.).

In one of your picture are some died twigs already.
With no foliage the flowers are not perfect healthy, usually will not set fruit or if they will, then will be dropped later.
You should concentrate to have dense foliage, the flowers will slowly down the new grow.

I’m not recommended anything I just share with you my opinion, it's your tree and your choice.

I've already cut all the buds and flowers of. Thanks for the help .

Since 2 weeks I've been cutting of the buds of my chili peppers too. They lacked growth.
So considering that I see the logic in cutting of the buds as you said.

I wanna say it's a root problem as I can see slot of die back. What's your soil mixture?

The mixture was dcm mediterra soil but has changed this weekend to dcm mediterra+perlite+sand. The roots looked very good.

Just in case it would be some sort of disease I searched google.
This site gives some nice information about citrus diseases.
For some reason my citrus could relate very much to the first disease.
Also citrus greening (a little further down below) looks interesting in my case.

http://www.ipm.ucdavis.edu/PMG/C107/m107bpleaftwigdis.html#CLOSE