Hi there!
I have 2 dogs and one foster dog. Two of my dogs have been going to doggie training classes separately so they respond to my commands very well.
The foster dog that didn't even know "sit " command, learned it by looking at my own dog. However, if you really want each of your dogs to master basic commands, I think you ought to spend time with each one individually. After they all master those commends, you can maintain/refresh them all together.
When you teach commands you want to have your dog focus on YOU not the other dogs. The other dogs are very distracting so it is hard to get his/her 100% attention. Once he master it, it will be easier.
I am now training my dogs to follow my command, one by one. I have my two dogs sit in a distance and tell one of them to "Wait" and the other to "Come". To follow "Come" command is easy but "Wait" while the other one moves takes a lot of self control. I can also have one "Stay" while the other one to go fetch a ball. Once each of your dogs master the basic commands you can try that too. It would be challenging for both dogs and you
