Agreed, the male needs to be kept separate from the female (far enough away so that they can’t mate through their habitat bars, which is definitely possible if they’re kept in separate cages which are still too close together). I’m glad to hear, at any rate, that the babies seem to have made it through the critical newborn phase; we have a lot of sad stories here about accidental litters where at least some or all of the babies pass within days, which is all too frequent with first litters.
Being that they’ve made it to four weeks, presumably they’re overall healthy and well-fed. They should be ready to wean in another month or so, so get ready to start introducing them to solid food if you haven’t already; they will need alfalfa pellets and alfalfa hay (for the protein) to about 6 months of age when they can start transitioning to timothy, and they should also be introduced slowly to greens during this time (slowly, to get their systems accustomed to vegetables and to find out what they like and don’t like). Their mother should also be getting alfalfa while she’s still nursing her babies, also for the protein.