Don't just do a swap for a 24t chainring. You are already at the maximum capacity of your rear derailleur and unless you get a smaller big chainring or smaller big cog, you'll be over your capacity. I use and reccomend a 44/32/22 crankset with an 11-34 cassette.
You're also at the maximum capacity for your front derailleur but going over on the front isn't as bad as on the rear.