7 year old severe stutter / ADHD medication

7 year old severe stutter / ADHD medication Hi, my 7 year old started with a bad stutter when we were overseas visiting family in May last year. Once we got back home to school we got him SLT sessions once a week and that reduced it down significantly after about 3 months, however just before Christmas he started again really bad - lots of blocks and facial tension trying to get his words out. Its exhausting for him. Since about September he has been diagnosed with Adhd and we have been trialing him on different meds (Ritalin and Ritalin LA). Could these meds be making the stutter worse? Are there any vitamins shown to help stuttering? Thanks