Hyperkalemia is a common side effect of these medications. GI disturbances, including nausea, vomiting, diarrhea, anorexia can occur. Triamterene and spironolactone have been known to cause impotence and sexual dysfunction. Spironolactone may precipitate gynecomastia or an SLE-like syndrome.
Flexeril has a half life of 18 hours. So 5x18 is 90 hours. Or just under 4 days. Of course, it is not that easy. This varies on how much and how long the drug was taken and it can vary from person to person. That being said I cannot image any way that flexeril would be detectable 30 days after the last dose.
Flexeril can occasionally give withdrawal symptoms of nausea, headache, flu like feelings, and trouble falling asleep, if you have been on it for a while. I've been on 10mg for 2.5 years and haven't really slept in the last 3 nights since I stopped it despite taking other medications that normally knock me out.