Yes, it does look like fluoride toxicity.

http://extension.psu.edu/pests/plant-diseases/all-fact-sheets/dracaena-diseases

Does the pot have drainage holes? 4 cups may be too much.

How do you check to see if it needs water?

its either related to chemicals in the tap water or overwatering.

Note: 50 feet from a window is just about as good as no window at all.

Office plant I take it?

Yes it is an office plant, I'm a plant technician. The plant has drainage holes but also has a liner underneath. It's hard to check to see if it needs water because it is potted in lava rock. I didn't think that 4 cups was too much because it is a 12" plant but you may be right

I'm not familiar with fluoride toxicity, but the link says the brown stripes affect the white stripes on the leaves, but it looks like your problem is at the edges, including entirely green areas, of the leaves. It shouldn't be hard to get the results of water tests done by your local water authority; ours even posts them online. This will also tell you how hard your water is.

Is the lava rock a top dressing or is it part of the mix? Is the mix fine and peaty? Are the damaged leaves limited to one branch or to the top or the bottom of the dracaena?

The size of the plant would affect how often you water; a plant that large in that sized pot will dry that amount of soil pretty fast so you'll have to water more often. On the other hand, the amount of water you give it each time mainly depends on the type and amount of soil in the pot.

Make sure that the bottom of the pot isn't sitting in drained water, which will allow minerals flushed from the soil to reenter the pot and keep the lower part of the pot saturated with water, which is deadly to roots.

As you probably know, dracaenas love lots of light. I've seen them thrive directly under bright office fluorescents, especially if the lights are on all or most of the day. You're dracaena's corner looks very dark, though, so I'd move it directly under a set of lights to keep it in good condition.

I hope something in there is helpful.