Can a tank be "too crowded" where the nutrients are all used up? Also what to look for in water chemistry thats best suited for planted tanks?

The answer is YES.
I'll contribute another time. It's going to be a discussion longer than a few sentences.
You know about the "Estimate Index" of dosing fertilizer?
It is pretty much the same with any level of lighting. Just that lower light require less nutrients.

Ken, if you don't have already, I suggest you get some Excell.
This is a liquid carbon source for plants. And you can use it to destroy unwanted algae growth. You will need a siringe to apply a direct squirt on patches of algae. I stress so much on algae because when we start out, we haven't gotten the touch or feel for the ballance of light, carbon, and fertilizer yet. This imballance of elements what gives algae an advantage to grow. Yes, they grow extremely fast. And sometimes you may even need to remove all the plants and scrub them off the leaves.

yes, light, nutrients and CO2 have to be balance, this is also depance on what plants you are keeping.

a balance planted tank, nutrients = 0 :)