ccs styles don't seem to effect headers in text blocks

Hello, I have a troublesome issue that I can't seem to work out.

Currently, if I change the header fonts sizes in the customise selection I seem to be able to change the style globally which is great, however, if the text has been added in a text block (wp Barkey) the rules don't seem to apply and I end up with an odd bold on the h2s. I've checked and I haven't set any css to override it or anything, any ideas what this might be? thank