Olive tree wilting

Hi there 

We ordered a couple of young olive trees a couple of months ago 5ft in height. We planted them in the ground about 6 weeks ago.

ive taken a look at them this afternoon and they are showing some wilting ok the end of some of the branches. Should I be worried? Hoping if there’s something I have done wrong then I can try and fix now while it’s early days!

we had been watering them every few days and now we water them approx once a week - about 5l of water per tree. I haven’t fed them yet but plan to in june.

wondering if anyone has any advice as to the wilting/ what to do?

Thanks