Dieing mushrooms

[Lego]

Some of my Mushrooms are dieing in my tank. Any reason why? I was reading the PH level would cause a problem but I tested it and it was at 8.3 according to the guide that came with the kit it says it is fine. I did get my wife to do the test and she knows less than me so that isn't a very good start here. But I trust her

My Nitrite are HIGH so there will be a massive water change tonight too.