Were you sailing with an overlapping headsail - if so I would think the
jib was not trimmed closely enough as the main shows no backwind, or the main is overtrimmed - can't tell without seeing the telltales on the backside of the sail...
You might remove the luff telltales, they are useless on the main, move them to the belly of the sail, and you should locate the leech telltales so they trail off the leech in open air, that way you don't have to look at the back of the main to monitor proper airflow.