It looks like you're learning too many new words. Maybe try to do 2-5 new words a day? Accuracy aside, chances are you won't be able to keep up with your daily reviews if you keep adding 20+/day.
I'd also recommend doing a few rounds of reviews (from "Focused review") for "Missed recently" after you're done with your daily reviews :)
Like ギョルギ九十三, you can slow down if you want. This will allow your brain to focus more on fewer words and it will be easier to maintain a higher score. With time, you will be able to learn more words at the same time, so there is no need to worry about speed too.
Also, renshuu (and similar app) are a great tool for learning japanese but there are not perfect either and only using them is not the easiest way to learn. It's better to use moderately and at the same time, try to do some more complex exercises like writing or studying words in context. It's also a good things to take break between clearing schedule to work on the words you learned. Or before you learn a new batch of words, you can take your time to look at the words, how are they used in context, etc. It's seems like nothing but it can help a lot just by clarifying the meaning for example. Writing all of the words the day before learning those words can help.
At the same time, blocking the difficult words can also be an option. Some words are just more difficult than other and it can better to just study them separately with additional methods (like writing).
It may look like a lot of things to do but once you find your rythm and favorite methods, it's much easier. Some people like to write, some people like to learn words in sentences and never out of context, etc, etc
