Wellspring looks to be bugged for some people and not giving rewards. I have run wellspring three times (once on attack, twice defense), and gotten nothing out of the chest but glimmer every time. Additionally, the powerful reward was not rewarded to me either on the third completion, but the director was tracking my progress, and it is now gone from the director as though I earned it.
Others on reddit are reporting this as well: https://www.reddit.com/r/DestinyTheGame/comments/szveeq/the_wellspring_defend_weekly_powerful_not_dropping/
I think I have found a possibility as to why we may not be receiving any rewards. I never received any of the gear from Fynch, but just to test it I grabbed one piece of it (the arms) and now I'm getting rewards every time I complete the activity. Either the daily weapon or the arms (even sometimes both). So the more gear you have unlocked with Fynch and actually accure it the more possibility for the rewards at the end.
Hope this helps everyone. I hope that this is the issue cause this worked for me.