Experts and BHG readers answer.
Yellowing leaves on Hybrid Tea Rose Bush
It's hard to say for sure without seeing your plant, but hybrid tea roses such as Mr. Lincoln often get a disease called Black Spot. To combat this disease you need to spray your rose with a fungicide every 7 to 10 days through mid-summer. Also, remove all diseased foliage and branches and never water from above. It also helps to grow disease-reistant roses. Mr. Lincoln is a very old variety that has little disease resistance. Although the variety has pretty flowers, I don't recommend growing it anymore because there are many newer red roses that are more vigorous and easier to care for. "