We are sometimes mining coins that are so fast that they will always result in higher rejected ratio. I make sure we are mining them only if their profitability is so high that it makes up for hashpower wasted on rejected shares, so you shouldn't worry when rejects are temporarily high again - it means it's worth it. Also, reducing intensity in your miners might help when we're mining low difficulty and fast coins (depends on GPU). I hope that our profitability is rewarding you a little bit higher rejected ratio.

I am still investigating if I can do anything more software-wise on my side to reduce rejected percentage regardless of coin type and its speed/difficulty. I have some ideas and will be testing them in my dev environment. Will keep you posted.