I think that’s an issue with employing your friends (or becoming friends with employees). Whenever friendships mix with business, it’s always a problem
I don’t think them asking for more money means they disrespect you. It’s like asking a boss for raise. It doesn’t mean I disrespect my boss. Negotiating and renegotiating is common. Sometimes you get more and sometimes you don’t.
I also don’t think that the fact that they have full time jobs and make more than you 9-5 is relevant. Unless they agreed to volunteer for you for free, what they make in other jobs is not relevant.
I think you have three options. Pay them more, pay them the same in hopes they agree, fire them and look for other people. If you feel they are asking for too much for doing too little, then don’t agree to their demands.
I do agree it’s stressful. Hopefully it works out so you could relax a bit