Kinghorn, 18, was making his first start for Edinburgh at full-back and his performance was one of the highlights for Solomons.
But ill-discipline let them down at key junctures and the head coach - whose side have now lost two in a row after opening their campaign with four wins on the spin - admits his team need to wise up.
"Last week we were disappointing but this week I thought we were much, much better but the penalty count played a major role," he said.
"We had six penalties in under half an hour - their first eight points were due to a succession of penalties.
"There were many positives, however, and Blair, who I thought was playing really well, got an excellent kick and a great run down the touchline.
"Even right at the death, though, the guys took their chances."
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