sir_isOanswered grow question 4 years ago Just inspect around that to see if there's not like a bug or mold or something.
Other than that, looks fine. I wouldn't be too worried about that, it might be light hotspots, aeration, heat causing it to get "spent" more quickly.
But as it is, it looks very minor, you can just pop that piece off a bit before the others (assuming it's clean) and use it as a sampler, coz why not?