My question is, is this tightness normal, or does it sound like I need to stretch more?

Research over the last few years has moved runners (and others, perhaps) away from static stretching as it's been seen to cause damage to muscles and reduces power output.
I have read comments from well-experienced posters that they stretch after running but what I've read over the past few years has convinced me that there's little value.

I know I am hydrating enough all week, but maybe I need more electrolytes during my run?

In a word, no.

MFP'rs love to drink water and GatorAide loves to get folks to pony up at the supermarket but our species is well suited to lose many pounds of water (with concomitant loss of electrolytes) before we need water, much less additional electrolytes.

I'm not arguing that we shouldn't cary water when running under demanding conditions but, unless you're doing lots and lots of miles in high temps, our body does fine with a water deficit. Multiple studies show that the folks who lose the most water during a marathon, for example, are those who have consistently lost the most water, for example.

My profile picture shows me running (a Half) with a water backpack and, under some conditions, I still run with water. In my training runs, which only last up to about 2 hours, I've found that drink no more that 24 ounces, even as temps hit the 80º mark.

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So far I have no[t] increased my weekly mileage beyond where my pre-training base has been. I could just be overthinking everything, next week is a cutback week in the training program, so maybe I just need a little more rest. But any insight is appreciated!
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If your calves are "tight" that's an indication that you're putting a lot of stress on them and that they are recovering (that's how we get stronger). A lot of people use a foam roller and research indicates that, similar to massage, a foam roller can speed recovery.

I'm Queen Tight Calves.

Foam Rollers are okay, but what you really need is a Trigger Point Starter Kit, or if you're not able to be that spendy, a tennis ball and a yoga block.

One of the best investments I've ever made: http://www.tptherapy.com/Starter-Set_2.html

Here's a set of videos from my local Fleet Feet with instructional videos on how to use it (first three videos - you can sub in a ball and block): http://www.fleetfeetsacramento.com/videos/trigger-point-therapy

Also, make sure you're properly hydrated, and pre-salt if you're a salty sweater.

Google "The Stick," it will change your life!

I had the same probably early on during my marathon training, and my foam roller saved the day!