"The Non-Designer's Design Book" by Robin Williams.
I am not a designer. But I am getting better, a big part due to this book:
Even though it is not aimed at online it is really really good at pointing out some of the very simple and immediately applicable things 'designers' do to make things look better.
e.g. one example if you want two complementary styles of text, make them very different - much bigger, or one much bolder, and a totally different font. Or another could be always making sure things align with something else, you have placed it there for a reason. It all seems very obvious in hindsight.
Also checkout https://refactoringui.com/ for a more modern web oriented approach it is pricey for the amount of content IMO but what is there is good stuff.
I think it helps with the prevalence of flat/simple sites even as a non designer you can make things look good by striving for simplicity and consistency
It's a paid course, but you can get coupons almost all the time for 10-12 bucks. Everything he teaches is excellent.
Robin Williams The Non-Designers Design Book
2 solid choices. I am a designer with 0 artistic skill. These will both help you make better design choices. Joe's Udemy course above focuses extensively on UX and UI. He also teaches a Udemy course specifically on UX/UI, though I found a lot of duplicate content between the two. I'd recommend looking at both of them.
A suggestion, because college writing, even for a tech comm degree, seems to be quite different from the kind of writing you'll do professionally: Read a lot of documentation.
You don't need to read it to understand the product or service, you need to read it to understand what different kinds of documentation look like. And to do this, you need to read a lot of documentation. A lot of documentation. You need to spend hours and days and weeks and months reading documentation. This is how you start to understand what good documentation looks like, and more importantly what bad documentation looks like.
Is the documentation easy to navigate? Can you logically follow from one step to the next? Does the formatting and font choice make it easy to read? What about the use of color - too much, not enough, not at all? Are the screenshots easy to understand? Do they use lists where a table would be a better choice, or vice versa?
For some of these, there isn't a "right" answer - it will come down to personal preference and also to things like corporate style guides. But the more documentation you read, the better you'll be able to create documentation that will be helpful to your audience.
Some places to start, just off the top of my head:
I also highly recommend The Non-Designer's Design Book. Documentation design is very important, and this is the best reference I know of. I use the principles in the book to plan the layout for anything I write.
The Non-Designer's Design Book
As someone who started off as a non-designer programmer, I taught myself UI/UX just by practising a lot. The two ways (that in hindsight were the most invaluable) I improved were to:
• Read highly-praised books on design fundamentals... These two literally changed the way I make / look at everything that is graphic design related: 1. The Non-Designers Design Book ; 2. Know Your Onions . The third I can recommend is all about making websites / UX and covers everything you need to think about when you're working on a web project: 3. Don't Make Me Think (Revisited) . All three are very well-reviewed and have changed people's lives.
• Copy everything you like the look of. What are your favourite web apps / pages / interfaces? What makes them tick? Try and copy sections that you like to give you a feel for how things should be laid-out. Most crucially, use a vector graphics program (I cannot recommend Affinity Designer enough, not least because it is insanely cheap for what it is), and copy as many icons / vector images as you can. Learn the fundamentals of bezier curves and how almost every piece of graphic artwork is made up of different combinations / layerings of shapes... Forget about fancy effects (e.g. shadows, gradients) at first, and just copy the shapes themselves. This was my biggest revelation and improved my UI ability to that of a professional standard. Once you realise that a fancy padlock icon  is just a rounded rectangle with a circle and triangle in it merged together, you'll start being able to recreate neat icons really easily.
If you don't enjoy doing any of the above, then hire a professional designer :) There really are no other 'ways of dealing with it' than doing it yourself or using a service. But trust me, it is well within reach to get yourself to a decent level in just a few months.
 - https://www.amazon.co.uk/Non-Designers-Design-Book-Robin-Wil...
 - https://www.amazon.co.uk/Know-Your-Onions-Creative-Businessm...
 - https://www.amazon.co.uk/Dont-Make-Think-Revisited-Usability...
 - https://cfl.dropboxstatic.com/static/images/business/homepag...