What is going on with these Astrophytum cultivar seedlings?

[zagoric]

Anyone know what's happening with these Astrophytum cultivar seedlings? Haven't grown past juvenile stage. Sown end of July. Tips showing orange/brown color. For comparison, I included pics of other seedlings from same seed batch down at same time.

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[Grimm]

My guess, which really is a guess as I lack experience in seedlings, is that it is some kind of sunburn.

[Onzuka]

Hi Zagoric.

In my opinion, they look exactly like they should do at that age. Patience is a virtue.

Steve

[Aiko]

My guess, which really is a guess as I lack experience in seedlings, is that it is some kind of sunburn.

Probably not sunburned, but coloured by sun light. If seedlings get burned, you will notice it! They would be gone immediately, due to their low body mass. Colouring of seedlings is not a bad thing from my experience.