URCHIN DROPPING SPINES

[kamuii]

i checked on my tank a little bit ago, and my urchin has dropped a ton of spines!!! i did a 2 gallon water change yesterday and by accident i had knocked him over off his rock and onto his back, so i flipped him back over and he seemed fine, just a bit ago i check on him and this is what i see
ignore the dirty sand bed please

there's nori in there for him and he was doing fine yesterday, is this from the water change? is it where i knocked him over or both??? should i take him out or watch him??? please help!

 

[KJ]

Water parameters?

 

[kamuii]

Water parameters?

nitrate is a bit high, around 60, i fluffed up my sandbed as well yesterday. alk is ideal ph is okay, always struggled with that. and no nitrite. maybe i should do another small wc? my tank was cloudy yesterday for about an hour or two.. i'm thinking maybe the sand caused a spike?