It's probably a new
bug "feature" with iOS related to user zoom - which effectively breaks how web browsers are supposed to actually behave by ignoring font specifications and resizing text to an "optimal" size for the screen on the browser.
The fact that it's doing it with Chrome as well makes perfect sense as Apple basically doesn't allow any actual other web browser engines. It's all Safari using the same rendering engine with different UIs.
WAP specifically does not specify font sizes as it is assumed that the phone will optimize the WAP page text to the most appropriate font size on the device itself (
note the CSS), so it clearly isn't a server side problem. This happens because iOS is too stupid to consistently render HTML without having explicit instructions, and even can't consistently render HTML when it does due to its desire to "optimize" the page for viewing on a tiny screen.
A solution to your problem is probably to either disable the zoom feature or hack together a javascript bookmarklet using info from the following two pages:
https://marcos.kirsch.mx/2012/04/29/font-size-bookmarklets/http://www.456bereastreet.com/archive/201012/controlling_text_size_in_safari_for_ios_without_disabling_user_zoom/My apologies though, I'm too lazy/indifferent to make the code changes to the bookmarklet for specifying a fixed font size for you. :)
You could also try filing a bug report, but don't hold your breath.