I've never seen them brown before... How old is it?

She said it's 3 months approximately, she neglected her plants a little and said it doesn't develop much, the plant is with me two weeks now and it shows new growths and looks happy.

This looks like no adenium ive ever seen.

Here is a picture of its "brothers" mine is the middle one

When seedling came to me, I've checked it's roots and was in poor condition, the soil was like clay, so I've changed soil and wash the roots, now is a lot better than when it came, but I don't know if it's an arabicum like she said, and what kind of arabicum it is