Here's what I'd suggest:
Definitely have a sit down with them (either together, or perhaps, individually) and explain that you're finding some of their behaviour at the moment difficult, self-centred, insensitive. It's possible they don't even realise how much their actions are affecting and upsetting you. Don't be judgmental or angry if you can help it, just say something along the lines of " I know you're not doing this deliberately, but I feel you're expecting a lot of me to make all these arrangements, and not really giving a lot back, and it also upsets me that you guys have let me down when I *do* arrange stuff for us lately. There's also been a couple of comments you guys have made recently that I've found quite hurtful, and I just wanted to explain to you guys how I've been feeling" type thing. Try and use objective phrases like "I think", "I feel", "that thing made me feel" rather than accusational,confrontational statements like "you did this, you did that" etc (if that makes sense).
Their reaction will tell you whether they're good friends and worth keeping (if they are upset/surprised at how you're feeling, and say "OK, let's work on this"), or if they're just selfish takers. It could be that their behaviours of late are due to other problems entirely in their life that you're not aware of, and they've been acting carelessly towards your friendship with them because of other distractions.
Also, if you do decide to initiate this kind of frank chat, appreciate that they may be having issues with you, too, and be prepared to accept criticism constructively. Could it be that the reason you're getting the brush off and slightly mean comments is that you have done something to upset them?
See, buddies are something that's relatively easy to pick up in life, and they come and go over the years, but good true friends who're there for you are harder to find. If they're deadweight and they simply don't care for your feelings, sure, ditch 'em or at least don't go out of your way to make a lot of effort for them in future, life's too short.
If they're good girls, and care, you can talk about this, and there might be a lot more behind the stuff that's upsetting you than you realise. And if they are truly good friends to you, then they're worth working this through for.