I wouldn't get overly concerned if just one day but I would definately be watchful of it's color and make sure it does not fade.
Water quality is good every thing is within normal range.
Sorry bit of a pet peeve but it might not be
What are the exact tank specs and how was the cuke
, a cuke
is a poor choice for such a young tank let alone two of them. One is plenty for that size tank. One thing to realize about these animals is you cannot really suppliment their feedings at all. They feed naturally off the system and can easily starve and die in such a young system. It is usually best to wait at least 1+ year(s) before adding one.
You might get lucky with one but I think two is pushing it 8) , personally I would return them both.