Whether you call them tics or stims, anxiety can make them worse. If the medications are making the anxiety worse or in other ways making them need (or able) to concentrate more, this can also make the stims or tics more prominent. But it is not necessarily due directly to the medications. Just an indication of the medications perhaps causing stresses in other areas of the child's functioning.
Sometimes these things are an indicator, not the main problem.
So if a medication makes them suddenly a lot worse, it is not necessarily that the medication is causing the stimulant or tic. But it is doing SOMETHING not good, and an increase in stimulant or tic is one measurable outcome.
Sorry to nitpick, but it is important to get the distinction right. And yes, some medications can directly cause a problem with stims or tics, but I think this is far less common than simply a medication reducing the child's ability to cope, and the child ramping up stims or tics as a result of that.
WHichever reason - an increase, especially a big increase, indicates a problem that needs to be identified and addressed.
But the stimulant is not the problem. It's just a symptom, as well as a facet of the condition you need to accept, for now. It will change.
Marg