Pondweed had some great suggestions, but I would recommend trying the Earthworms too. Your new Lotl may not have been fed bloodworms or anything like that where you got them from, not to mention live worms are tasty and full of nutrients!
You should be safe taking earthworms from your garden as long as you don't use pesticides or chemicals in it. Give the worms a wash and cut them with scissors if they're too large (longer than Murlo's mouth). You can either hand feed (which stops them swallowing sand if you have it, and also teaches them to look up for their food) or use a turkey baster or similar to put the food in front of his/her mouth. Give the worm a little wriggle and they should snap it off you no problem! The thing is that they need to associate you with good things - your axolotls will come to see you as the bearer of food, and get excited when they hear the top of the tank being moved (as this is a prelude to dinner). They will also watch you and follow you around the room. The best way to do this is to feed them - after this you and the food will be the highlight of their day!
I would suggest separating Murlo until he/she is as big as your original lotl as Pondweed said, mainly because there is a bit of size difference. You could use a divider for this, which will allow them to get each others' scents but not actually come into contact. You can make one very cheaply by cutting a condensation board (basically a sturdy piece of plastic) to fit, which usually costs £6 or less. I did this when I first got Galaxy, my second lotl. By the time I got Galaxy, Toothless was 7" and Galaxy was 5 and a half inches. I quarantined Gally for around a week (30 days is better really, but I was changing to a brand new 2 foot tank and decided to move them in together) and separated them using a divider for 3 days before letting them see each other. There were a few cautionary nips, but ever since, they've got on really well. They mostly give each other space but will sometimes swim and climb on each other, and can often be seen just hanging out in the tank.
If you want to use a feeding jar it does take a bit of time. Toothless wouldn't eat out of hers for three days and I started to get worried because she was only small at the time. I realised that you have to put the jar in and leave it (don't keep moving it around, like I did, as it only freaks the axxie out) and be prepared to be VERY patient. It took Toothless an hour and a half to figure out how to get into the jar, and longer to figure out how to get out. You can carry on feeding bloodworms by all means, but my two adore earthworms and they are meant to be one of the best foods for them, not to mention the wriggling may well stimulate Murlo's appetite!
Sorry for the long post, and good luck!