I had this typed out but it looks like I deleted it for some reason. If splitting your airline to each lift pipe doesn't make a difference then your air pump could be a bit small for that volume of water and the height it needs to be lifted. I have a 15 gallon cone bottom tank with a single lift pipe, and I use an AP 100 air pump that puts out, 2375 gallons of air per hour, or 9150 cubic inches of air per minute, or 150 liters per minute, or 2.5 liters per second, and the lift pipe is as short as I could make it while still lifting it to the top of the brewer. I posted a few pictures with a couple details about my setup in this topic New to Composting Tea
If you scroll through the topic you'll see that the OP Dennis, had to get a bigger pump for his 55 gallon vortex brewer to work. I seem to recall that some people were using multiple airpumps, one for each lift pipe, for their larger brewers.
The size of your airlift pipe makes a difference too. I built mine with 2" pipe because I dump everything into the brewer instead of putting it into a filter bag, so I wanted to ensure that all the particles could flow through the pipe and not create a plugged pipe. I've put fungus covered woodchips in it, the smaller chips, not the ones that are 2-4" in length. Also speaking of plugged up lift pipes, that is potentially an issue as well which is easy to verify one way or another, by running water only first to see if the vortex forms. With a smaller pump to a larger volume brewer, it may take a few minutes or more before you notice a vortex forming And if it is forming a vortex with water only, then dump in your ingredients slowly instead of all at once so as not to create a plugged up pipe.
I should get some video of mine, I had some at one point I just can't find it, the setup I'm using creates a vortex so strong that it reaches the bottom of the tank....or at least very close to the bottom from what I recall. I'm about to run it again here in a couple weeks, maybe I'll get some video.
A few things to ponder and play around with to help you create a nice vortex. The diameter of the lift pipe as well as the height of it plays a role in how well it works. The volume of your brewer is important to consider. And the size of your air pump is also an important factor. If you play around with those things you'll find a nice medium ground where you get a good vortex.