The potted dahlias that are sold are usually either bedding Dahlias that only get to about 18", or they are treated with growth inhibitors to keep them short.

Most Dahlias are 3.5 ft - 5 Ft. tall. Many of mine grow more like 6-7ft due to lack of full sun.

Most people "top" Dahlias after the 3rd or 4th set of leaves. Meaning they break off the central growing tip. It forces the Dhalia to bush out more instead of just growing one long tall stem. Most Dahlias need to be staked well to keep them upright.

Yours looks a little spindly from not being topped, but otherwise fairly normal.

In most parts of the country people don't expect blooms until late June early July at the earliest. Most of mine won't bloom until August here in WI.

I would go ahead and snip off the growing tip to force the lateral growth, but I have to admit that it will slow down the blooming time - still, in the long run you will get a stronger plant with more blooms.

Does seem pretty leggy...maybe too much shade ?

Thanks so much for your response! :) That helps a lot. So I guess I'm gonna be cutting off quite a bit off the top. I have 2 more but they aren't nearly as tall, but they probably need to be topped also.

And they do have quite a bit more shade than I intended for them to have. The flowerbed they're in is a new one and I thought there was at least 7 hours of sun but it's more like 4-5 hours.

4-5 hours of sun is pretty minimal for Dahlias. They will probably still bloom, but you won't get a lot of blooms and the plants will definitely be taller than usual. It is early enough that it might be worth moving them to a sunnier spot if you have one. I grow mine in 6-7 hours of sun, and wish I had 8-10 hours.