Rubber pleco died

[Darren86]

Hi all, I bought a rubber pleco a week ago today, I done a water change 2 days ago and the next day he was acting strange. He was on the gravel breathing rapidly, i hadn't seen him eat previous to this and he would just suck on the side of the tank (normal behaviour I assume). But after the water change he acted strange and this morning I found him dead on the floor. The strange thing is that he had black marks on his head which weren't there before. Any ideas as to what this could be? Thanks in advance

 

[Kat767]

What are the water parameters like ammonia nitrate and nitrite

 

[Darren86]

All parameters are fine, the ph is slightly high at 7.8 and the KH is also but everything else in the tank seems healthy and active. Even had shrimp that have had babies!

 

[Kat767]

Maybe when you added the water back to the tank he got under the stream of water and got hurt. Or he might have been bad stock.