I have one of those as well, two, actually. One is just under 6', the other is under 4'. The 4' plant is a cutting from the 6' plant. I've had to cut down the taller one twice in the 7 years I've had it and now it has two "shoots" that have grown out from just under where it was cut the second time. I'm not sure of the exact name of it, but I've heard of them being referred to as "corn plants" probably because the leaves look like the leaves from the actual corn plant.
They do flower, but it takes them a long time to do so, but they don't have traditional looking flowers. They look more like small clumps of millet, for lack of a better description. The pot looks fine, but I would suggest a different soil. The soil you have them in now looks very gritty. Also, cleaning and dusting the leaves will help them breathe better and would grow better as well.
Miracle Grow is good, and will work but don't over do it. I've been using a well balanced liquid formula in the small green bottle every couple of weeks but using the fertilizer
weakly. I've also used the old adage of watering weekly, weakly.
I hope this helps you. Have faith...they will grow and in a few years, you may find you'll have to cut the tops off and plant those. Don't worry, the tops of the parent plant will grow new leaves. If you would like me to post pictures of mine, I'd be happy to.
Forgot to add one more thing. When it does come time to cut the tops, do so about 1/3 from the top and then immediately put the top in soil and water well. It will grow a root system and keep growing on its own.
Here's an image of mine. There are three plants; the parent and two cuttings. Hopefully your's will get to be that large.