Seems like you're doing well, and have half your expenses generated from the R.E. mortgaged at extremely attractive rates. Rent increases will over time have a disproportionate impact on cash flows due to your relatively low-rate fixed payment. In particular, you are loaded for bear with regard to the risk of inflation/stagflation, as almost 100% of your income derives from inflation-adjusted or inflation-adjustable sources.
As others noted, it makes sense to max out the Roths and you'll have some left over for traditional IRAs. Expect the cash flows from your properties to increase over time, generating a snowball effect that will eventually max out both your traditional and roths.
Key Risks to Manage:
1) One of your rentals burns down, and you go months/years without rent while waiting for insurance checks and contractors: Study your insurance, consider banning smoking/candles, etc.
2) Lawsuit from tenant: Manage with umbrella policy, LLC, and maybe an existing lawyer relationship.
3) Failure to raise rents to market rates: Conduct a market survey and secret shopper competitors' properties every few months.
4) Failure to maintain/remod properties, leading to falling rental demand and loss of portfolio value: Establish a maintenance plan/budget. Inspect properties on a regular basis to prevent problems from snowballing, and write this inspection obligation into your leases.
5) You're not really at economies-of-scale levels, and today's high RE prices and mortgage rates may have essentially blocked you from expanding your business. Maybe that's fine because you only intend your RE business to be part-time, and have a durable separate source of income. But it is a limitation, and highly-positive cash-flowing property opportunities may not be available again for many years. Similarly, we have to wonder if a good refinancing opportunity will ever appear again, or if in the long run you are heading toward a 100% equity position on these properties.
6) You don't mention your age, but eventually you'll get too old to manage these properties. Think about your exit plan. Do not execute your exit plan after you are already behind on a bunch of things - execute it before things ever get that bad. This is a common landlord pitfall.
7) You could face rising delinquencies or vacancies during a severe recession. Set aside plenty of cash outside the LLC so that you can use paid-in-capital to keep up on maintenance and stay liquid during such times.