I have a stuck fermentation problem. I'm making the Affligem Noel clone from Beer Captured. My OG was 1.090, FG was supposed to be about 1.018. I made a 1 qt starter of WLP 570 Belgian strong ale yeast and pitched 3/4 of it, getting very rapid start of fermentation. I saved a cup of the starter in the fridge for priming with extra yeast a few days before bottling (per the recipe). 3 days ago (2 weeks into fermentation) I checked the gravity and only found it to be 1.038 or so, and no evidence of ongoing fermentation.
I boiled up a combo of 2.5 tsp yeast energizer, 5 tsp yeast nutrient, 1/2 cup (about 3.5 oz) turbinado sugar, and 2 cups water, cooled it to 70 deg, and pitched it 3 days ago. I got a little boost in fermentation, bubbles in the airlock every 7 sec as the most brisk, but it didn't last long. 3 days later the gravity is now 1.035 with no further bubbling in the wort or airlock.
So the question is, what now? I'm at a loss as to why a strong ale yeast crapped out so soon, especially since I made a starter. I've never had this problem with Belgian high-gravity yeasts.
The options I see are:
1. Keep waiting and checking gravities for the next few days, maybe this is just REALLY slow fermentation
2. Toss in the saved remains of the Belgian strong ale yeast starter to try to re-boost fermentation, keeping in mind it's been 3 weeks since I first cracked the vial
3. Pick up a new vial of WLP 570 and pitch either the vial or a new starter of said yeast
4. Add champagne yeast to finish fermentation.
I'm slightly leaning towards option 4. Champagne yeast has helped me out several times with prior high gravity brewing issues. Any suggestions on these options, or other ideas? Thanks!