Avocado hard and grey inside

I had a batch of avocados from the supermarket, as I normally do.

I often have 3-5 days before they’re past the point of being edible.

This batch was not more that 2 days old, and three out of five looked like the avocado below (this is probably the best of the bad bunch), despite being firm.

In fact I felt like I was being a little cheeky and risking opening an unripe avocado.

Is the greyness from damage or disease?

I tasted one, and rather that tasting over or under ripe it was just bland.