Hello!

I'm sorry to hear about your hollyhocks. If you could upload a photo we might be able to tell more for you, but I can say now that the most common causes of yellowing leaves include nutrient deficiency (particularly nitrogen and iron), worsening drought (which would cause the plant to reduce its leaf number, prior to which, if possible, it will reclaim nutrients from them and cause the yellowing), or overwatering (which can artificially create nutrient deficiencies as the roots become unable to absorb them).

Consider checking the soil conditions around the plants to evaluate if they are overly wet; if not, a balanced fertilizer may help.

If you can describe a bit more about what you're seeing (for example, is it all of the leaves, just the upper or lower leaves, when did it start, etc) or send a photo we might be able to figure out what in particular is going on.

I hope this is helpful!

Cordially,

John

Thank you for the photos!

That is unusual.  The plant doing well immediately adjacent suggests that it may be an infection rather than an abiotic problem with the soil.

Yellow/green mottling, which looks like it might be what's happening based on your photo, can be caused by Tomato Spotted Wilt Virus, or TSWV.  TSWV can also infect mint, and would cause similar symptoms; this may indeed be what you're dealing with.  In order to confirm this, though, you would need to submit a sample to a plant diagnostic laboratory, for example the lab at CSU Spur in Central Denver.

Sadly, the treatment for TSWV is removal and destruction of the plant.  It is spread by tiny insects known as thrips, which are quite common and difficult (if not impossible) to eliminate in a landscape; removing infected plants can help to slow or stop the spread of disease.  

I hope this is helpful.

Cordially,

John