After 3 week primary, beer is slightly under-atenuated. Tips?

Hey guys,
I brewed a Brewers Best Belgian Tripel kit on December 16. I didn't trust the freshness of the LME so I replaced it with fresher stuff from AHS. The recipe caled for 6.6 pounds of LME, I ended up using 7. Also, the recipe had 1.5lbs candi sugar, I used 2 pounds.

It came with a pouch of dry yeast, which, since I was planning on adding a bit more fermentables than specified, I made a 1.6l starter with. I know, probably not necessary but I figured it couldn't hurt.

It fermented at a relatively stable 60-65 degrees, although last week I did notice the thermometer on the fermenter at 58.

Well, its been about three weeks, so I decided to open it and check it out. The recipe calls for a FG of 1.016-1.019. When I checked it, it came in a t 1.020.

So I would like your opinion, transfer it to bulk storage, since it is ever so close, or let it go another week and transfer next weekend.

It tasted delicious, but a little on the sweet side. Definitely tasted like it would age very well.

Thanks!

You added more fermentables, yes but along with both LME and candi sugar come unfermentables. The fact that you ended up just a point high of the upper range, I'd say you're doing well. It is probably done and no more mucking about will improve the beer. Try to carbonate on the higher end, which might help offset that sweetness.

And if you are planning on aging anyways, you never know. I made a Dubbel and a Dark Strong at the same time, the DS finished at 10 ABV but with an FG on 1.029, the Dubbel 8% with an FG of 1.020. Both higher than I wanted, but now a year later the Dubbel is way sweeter tasting, while the DS is pretty drinkable. Go figure.

if you made a starter with dry yeast, that's most likely your problem right there. that saps those cells of a lot of their energy, meaning you probably underpitched pretty bad. they've been designed to just need a rehydrating to get going.

What kind of dry yeast was this? I'm not familiar with any good quality dry belgian style yeasts...

Also, +1 to not making a starter, dry yeasts have nutrients built in and are most vigorous out of the package