Are banjo bolts grade 8?

Good morning folks,
I have put new calipers and brake lines on my Duster. One side continues to weep a little brake fluid at the line to caliper connection. Yes, the copper washer are there, you can see them both (one between line & caliper, one between the bolt head and the line. I have really tightened and retightened it. I am afraid to get a longer wrench on because I don't want to break off the banjo bolt.
Have I overtightened it and need to try a new copper washer?
Any other suggestions?
Thanks,
C