Purchased timber black at the ends

[Johansjuu]

Hello!
I've purchased 70x22 boards for a fence.
They were stored outside under a tarp where we bought them, so they were a bit damp. They have now been in our garage drying for a week.
I noticed now when we were about to start oiling the boards that they are dark at the ends.

What could this be due to?

 

[AndersS]

Don't you have a saw so you can cut off a little of the ends? It won't be many cm and a little discoloration remaining doesn't matter.

 

[Stefan1972]

it becomes like that if it is exposed to rain and then dries and gets wet alternately.

 

[Johanbogg]

Like sweat stains on a light fabric upholstery in cars