Failed Asian Pear Grafts- fungus?

Hi All, I grafted 5 pears about a month and a half ago- hosui onto OHF97. 4/5 took. About two weeks ago, I noticed that two of them stopped growing, and took a turn for the worse. I now have one left, that looks decent. However I think it has black spot fungus. Do you think the grafts failed because of early onset of the fungus? See the photos attached if that helps. All were watered once a week, so I’m suspecting the fungus did them in. Thanks all in advance for helping me diagnose what went wrong, so I can do better next time!

I don’t know about fungus issues- in my climate we’re largely spared those. But that bottom one looks suspiciously like fireblight to me.

WARNING: I see fireblight where there isn’t any, so don’t depend on me for this!