Liop, that's sun burning damage, it seems that they were standing in a hot place to long.
The only thing you can do is put them in a more shady place.
After doing this they will grow happily ever after...

Sometimes I'll see quite a bit of variation seen in plants growing in similar conditions, and it can be difficult to pinpoint the cause (or causes) of the problem.

I can't say what's going on with your spruce needles, although for seedling germination I would recommend something other than plain potting soil.

This mix drains quickly and allows air to get to the roots.

Perlite, scoria, turface, small bark fines, and a dash of potting soil. There are other variations on this theme.

Good luck!

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i dont even think his is a mixed media.. it looks like straight peat ... they will soon need to be in a high drainage media ... similar to sluices.. or a cactus mix..

there is also Al gritty mix.. all over GW ... try the search function.. if no one else links you ...

i agree on sunburn ... or perhaps the dark peat overheated.. and heat burned them in sun ....

seedlings that size.. should probably be in very bright shade.. rather than sun ...

ken

if it is straight peat.. there may be pH issues ... though i have no idea on omorika ...

ken

Thanks for the answers.
They may indeed have burned a bit since it was very hot here the last days. I will try to put them in half-shade instead of full-sun.

I will also try to make a better drained soil. I presume it is also best to put the spruces in a pot with holes in it? The pot they're now in is fully closed.

The pH of the potting soil should be slightly acidic (according to the package).

Again thanks for the suggestions.

Yep, make sure the pot has holes in it.

Please keep us posted on their progress!

I took the advice and changed to pot they're in:
I made holes in it and placed it in the same kind of pot so it won't make our house wet when indoor.
I changed the soil with one made from gravel, pieces of bark and potting soil. The top consists of a small layer of potting soil with some gravel on it, just for aesthetics. :p

Here is a picture:

Update:
I just watered it and water came through the underside very fast. So I presume it drains now a lot faster than before. The water coming through the underside was quite dirty though (taking some potting soil with it), so I'll have to add potting soil quite regulary.

I've put them in full shade now because it's what they call the "hottest day of the year" today. Temps are going up to 35 degrees Celcius (95 degrees Fahrenheit) which is exceptionally hot for where I live.