I have Erythronium Pagoda, it took several years to bulk up and flower but even then it wasn't a big plant and I know there was around three tubers. It's been very off and on, in 2010 I had a lovely large group which flowered well. It then disappeared except for a couple of leaves making an appearance, we had a very hard winter in 2010/11 so I'm not sure if that affected it, or nearly killed it. I might see another good display in a few year's time, maybe 2020?!
The leaves do look like young Erythronium, they have a sort of waxy appearance. When they flower it will make a superb show! Mine was in flower in early April.