You should reduce stress on muscles by doing lighter exercises. The tendon rupture may happen months/years after the antibiotic course.
I've been on 750mg levofloxacin recently and it was a nightmare, but maybe it was a die-off reaction of the targeted pathogen (it's active not only against bacteria). During the 2 weeks I took it, it gave me a combination of Parkinson (hands trembling) and Alzheimer (extreme forgetfulness of what I have to do in the next 5 mins). Thankfully, all these went away when I finished the course.
I've been on ciprofloxacin before and I don't remember such extreme side effects but maybe I wasn't that infected back then and there wasn't a die-off reaction. I also had a rotator cuff injury at the gym in 2012 but can't remember if I had a course of ciprofloxacin before that - I had one course in 2015.