YEAST Starter for All grain IPA 20 gallon

Thanks for the helpful information. I brewed a 20gal batch Pale Ale Saturday so I made a starter Friday night, 4Liter water, 400g light DME, yeast nutrient, aerated wort with O2 + 4 Wyeast 1056 ON stirplate for approx 18hrs before pitching.
After 90 min boil and cool to 70deg OG. Was 1.059. Aerated wort with remainder of bottle of O2. Pitched yeast Sunday morning, yeast was working very good. As of Tuesday night things have come to a standstill. I didn't want to take a sample last night but I'll check again tonight to see what the gravity is. I havent decided if I'm going to rack into secondary. Maybe I'm doing more harm exposing to air??????

I checked the gravity last night. OG was 1.059 Saturday night, 1.018 Wednesday night. This is the first time I've checked after only a few days.
Does this seem normal, slow or fast attenuation?
Should I transfer to seconday or not?
There's also a lot of sediment at the bottom of the fermenter.

Don't turn your nose up at dry yeast. If you are making an American IPA just get 4 packs of US-05. It is pretty good stuff. Dry yeast is much better now than it was years ago. I do this all the time when I don't have time to do a starter. It works very well.