I would take a hard look at the numbers for each property to see what's worth keeping and how much you should continue putting into the fixer upper.
You mention that the rent covers the mortgages, but does it cover your other expenses and budgets as well? You should budget 6-10% for property management, even if you're doing that work yourself, plus vacancy, maintenance, and capex. I use a back-of-the-napkin number of 25% of the rent for those four expenses. Do you get any cash flow after your mortgage (assuming your payment covers taxes and insurance in escrow) and that additional 25%? If so, that a good start and they may very well be worth holding onto.
For the fixer upper, you should look at those same numbers, but also look at the cash on cash return of putting in additional money. Basically, take your annual cash flow divided by all the money you've put into it, including down payment, closing costs, loan fees, and the costs of fixing it up. Where does that number stand today without fixing anything else? If it's over 10% and you're almost done, it's probably a good investment. If you're at 7% or under, it's verging on being a bad investment, especially if you have additional fixes to make. You can also use this number to figure out how much more to invest before your returns start dipping too low. You could calculate this on your other properties as well, but it's generally used in due diligence prior to purchase, and since you already own them, I wouldn't worry about it too much personally if they're cash flowing well.