(source: EIA statistics)

What on earth am I supposed to do as this is a main income source for me as a good landlord?

This slowdown may effect your job / source of income.  2. 

What is the root cause? 

From the PM side, we have seen owners reach out with concerns about tenant's abilities to pay rent and tenants who have lost their source of income.

It still says rent is due and offers other sources to use that might help the tenant.  

RE agents who specialize in investors are a great source. 

By feeding the HELOC with all my rents and other income sources, the average daily balance stays much lower and the result is a mortgage that gets paid off way sooner.Have you heard of a HELOC credit line being shut down prematurely?

It likely goes back to the source of the funds they access.- If they own a bunch of homes and are lending from their HELOC...they don't want to be called on a bunch of those if price values plummet- If they borrow from another lender at a lower rate (even the 0% fed rate) with collateral tied to other assets...say the stock market...that's taken a hit, so they can borrow less. - If they have actual private lenders...which they claim they all do, but you'd be surprised how many don't...their private lenders may be going to cash and pulling their moneyYes, they need to lend money to stay in business...but if they themselves are getting squeezed, it'll come back to us investors 

I would NOT do a blanket loan today given so many DSCR lending sources are at even under 6% one loan on one house.