Forms labels showing <strong> and other HTML elements

I'm wondering if anybody has seen this issue before?

This morning I logged on to see that the Marketo forms on our website were showing like this:

I quickly edited the labels on this form and removed all evidence of the <strong> </strong> HTML around each label thinking it might be a unique error to this form, to discover that this has occurred on 80% of the forms in our Marketo instance, including the ones I built yesterday which were find when I logged off yesterday evening.

I'm seeking assistance from here as Marketo isn't allowing me to open chat, submit a support ticket via email OR via the telephone (after trying several times).

Any help would be greatly appreciated!