Nothing, keep practicing!
Out of curiosity... which string is standing out? As BrianQ states... learning a good strum takes time.
Forgot to ask if any of the strings are harder to hold down? If that’s the case, then inspect your Bridge/Nut to make sure its setup is not too high for chords? If it’s too high, then you can find old threads about setup by using the Search box up at the very top of the page? You can usually lower bridge height by flat sanding the bottom side of it? If it’s not a setup problem, then, as I said: practice more so you can develop those finger muscles.
Number of strings, 6, 4, 3? Action height?