I have a suggestion for judges at every level, from middle school festivals to the Met auditions:
You are on the best ground if you report on what you hear, without giving ways to fix it. You do not know the context of that singer’s study, their history, their challenges, nor their ability to translate your words into action. However, you can easily and clearly convey your impressions about that performance as they relate to standards, performance practices, and areas for growth that they need to address with a teacher. It is of immense value for the singer to read about what an experienced professional is hearing. It is often confusing to dwell on how you would “fix it”.
Spend all of the limited time you have at the judging table conveying what you hear, and perhaps why what you are writing about is important. That is the most bang for the buck that you can give with your service as a judge. Please save prescriptions for the master class and the private lesson. You don’t know the singer before you; you only know this performance.
“I’m noticing wavering intonation at the ends of your phrases.”
“You are taking more breaths than the phrase is asking for.”
“I hear a vocal sound that has much promise but is perhaps fighting some tension.”
“Your timing could be more free. Talk with your team about playing with ‘rubato’.”
“Your German diction has good consonants, but the vowels could be more specific.”
These are all things that are heard that can be addressed by the singer later. Judges need to be trained in a) how to hear (topic for a whole book!), b) how to write about what they hear, and c) how to stop after a) and b) because that is all that is needed/ wanted/ healthy/ constructive for a young singer.