Quote from @Morgan Gutierrez:

Is there a legal timeline to update current investors about a significant change in the investment?

What are the legal requirements for updating the investment information/pitch deck for new investors?

I am no longer working with this person, but am curious what the legal obligations are and if they were followed. It is certainly immoral to raise funds without updating the information on a deal, but is it illegal?

Besides certain reporting requirements being spelled out in the Operating Agreement, a lot will depend on the type of offering that was made when investors were given the opportunity to invest.  Assuming that the offering was a securities offering, as opposed to a joint venture, we’d need to know first if the offering was a registered offering or was claiming an exemption from registration.  In the much more common exemption from registration, was it an intrastate exemption, a Reg D filing, or did the offering rely on the general exemption for private placements?  
Your question does bring up a very good point.  Few investors realize the differences in the types of the offering.  More sophisticated and experienced investors, and those employing knowledge attorneys will understand that while not an absolute, a REG D offering offers some amount of comfort in that the sponsor has placed his offering on a more “sophisticated” level than an intrastate or general exemption offering.  Many larger investors won’t consider any non registered offering unless the sponsor has file and follow the rules for the “safe harbor” Reg D offering.