Home brew tasted fine before keg

[Dilligans]

Ok I kegged a saision amber ale after in the primary for three weeks. I tried it before I kegged it and it was great. The starsan the hell out of the keg then kegged it. I then let the keg sit at about room temp 72 degrees for three days. Put it in fridge for 1 day and taste a little apple?

 

[Dilligans]

The beer was not fully carbonated yet but cold? What could this be.