since you didnt cycle this tank first, and immediately added about 13 females the same day/week...........id be VERY careful watching your ammonia levels now. they most certainly WILL spike. my suggestion..is to change half the water every 3-4 days until u keep the level safe and the tank actually cycles which can take up to 8 weeks or so. id also highly recommend adding AQUARIUM salt.
if not, then be on the lookout for very red gills, its almost ALWAYS a sign of ammonia poisoning. if u see that, immediately change 50% water today, and 50% again tomorrow. then in about 24-48 hours the red gills should be just about back to normal.
and also, in my opinion, i would definately not add anymore than the ones u have. you have provided lots of hiding spots and everything but they will gro to about 2-3 inches each. thats ALOT of fish bioload for only a 20 gallon tank. i would have suggested 8 - 10 maximum.
these are only MY opinions and please dont take offense. its not meant that way. ive just learned alotta things the hard way. so if this can help prevent some illnesses or deaths for you, then great!