I second that. Also, khulis really need a group... say 4-6. The more the better. I'd also round out that single cherry barb (as they prefer company too) and make a trio (1m, 2 fm) and maybe even add a few more glowlights.
HTH!
make sure you look out for the welfare of your fish you have at the moment.
do not add a rtbs, they will disturb your tank, when they get bigger and more established in your tank they will be very territorial and will take over and guard a good part of the tank and make other fish stressed.
if i was you id make up the numbers of the other fish as there are a lot of fish which need groups that are on there own or need a bigger shoal.