I was position 4 and 11 for a keyword and now I’m nowhere - the only thing I think I have changed is adding a tab to four products, calling it delivery, and pasting the same delivery information into each. Yes it’s the same content but it’s just delivery content. In the checkout funnel, some abandon to look for delivery info, so I’ve added it to product info tabs as well as being in the main menu alongside about us etc. Is that likely something google wallops sites for doing?
We need to be very careful with websites, mainly because they are measured by a software process (bots) not humans. With so many people attempting manipulation often people working ethically get penalised.
There could also be another reason for the drop, it just coincided with the amendments you made
Without looking at the page itself it’s hard to judge, but I seriously doubt it was because of that delivery information.
It’s worth remembering that there are millions of other sites out there competing against you, and any change in your ranking could be a result of that. There could be a million explanations as to why this has happened, and I’d say that 99% of these couldn’t be guessed.
Regardless, do whenever you need to your site to make it work better for your customers. Eventually, if your site is good enough, it’ll rank well again.