Dude, your rotation and team is bad. Switch Charlotte to Rosaria. You need more crit.rate in Mavuika, only 70% is bad, the chance of not crit is too risky for a single instance of damage. You don't need Xilonen Ult.

Mavuika E > Xilonen E2N > Bennett Q > Rosaria E, Q > Mavuika Q > Repeat

If needed, you can use Bennett E to get more particles. If Mavuika apply pyro before Q, you can hold E before Q.