Our own rentals are under the same umbrella, so all business expenses, liability insurance, etc, is all for the same LLC company. 

Keep $300,000 on each house or more and a $1 million umbrella policy over all of them.

I carry a vacant home policy on each of my flips AND a 2 million dollar umbrella policy over everything I own.

Get an umbrella policy for yourself.At this point though, you need to determine if it's worth keeping your LLC or dissolving it.

We looked into an umbrella policy, but they insurance company said that we had to also insure our autos for more coverage.  

My recommendation would also be to get the highest liability coverage available on your landlord policy and then to follow that up with an appropriately sized umbrella policy considering all your assets, future wages and growth of both.

Nothing is foolproof, however, so carry a good umbrella policy -

Hence, they ultimately will out the burden back on you.My longtime mentor Frank, a self-described 'county seat lawyer' used to describe insurance companies like the guy who offers you an umbrella on sunny days but takes it away when it rains. 

I can't find anything about Umbrella Insurance among a group of investors. 

Most folks love the LLC to hold properties, but it doesn't really offer that much protection...you'd be better off with an umbrella policy or a rider.