Twenty Fourteen tables fontsize

Maybe the issue is specific to your website, I can’t see it on the demo site. Can you confirm? https://wp-themes.com/twentyfourteen

Andrew, There is a remarkable difference between the text size of the first sentence and the text in the table cells.

I have another table, made with TablePress. It has the same problem.
The css-code that TablePress suggests

.tablepress td {
	font-size: 16px;
	color: #000000;
}

does not work.
See:

Hopefully you can link your site so that we can see the issue, or link to a page on the demo’s site that has the issue.

I posted this link, but it did not show:

What plugins do you have? Try deactivating all of them to explore whether any are responsible.

The Styles plugin gives the problem.
However, when I deactivate it, all my customised colors, margins, etc., are lost.
What to do?

Override the Style’s CSS and not Twenty Fourteen’s CSS. Can you reactivate that plugin?

I reactivated it.

Use this instead:

.styles #content td,
.styles #content td p {
	font-size: 16px;
}

If that doesn’t work try:

body .styles #content td,
body .styles #content td p {
	font-size: 16px;
}

When I put this css in my Custom CSS Manager and decativate the Styles plugin, my customised colors are gone.

Activate your Styles plugin and then put that code in your Custom CSS Manager

Alas, I am now back where I started.

If that doesn’t work try:

body .styles #content td,
body .styles #content td p {
	font-size: 16px;
}

It does not work. I am back where I started.
Maybe I should take this up with the people from Styles plugin.