Jonagold apple tree

Hey guys. I'm completely new to gardening and have recently acquired an allotment. Safe to say i'm loving every minute. I've recently planted in a couple of jonagold apple trees...however think disaster has struck already. I've attached a photo...any help would be appreciated...has it already picked up some kind of fungal infection? This is one of the very very new buds appearing. Help!!

 

Hi @Emily Jones and welcome! All I can see is a flower bud (and a cluster of later ones around it) in the middle of a set of healthy leaves. What is worrying you specifically?