Fruit trees typically bear a lot of fruit and very little to none on alternating years unless the amount of fruit during heavy fruiting years is reduced. 

Your pear tree appears to have a fungal disease probably made worse by the hot, humid weather. I am not sure which one from the photos. Please check out the fact sheet to diagnose the problem. Samples can also be sent to the plant disease clinic for a positive identification.

https://portal.ct.gov/CAES/Fact-Sheets/Plant-Pathology/Disease-Control-for-Home-Pear-Orchards#:~:text=The%20diseases%20that%20are%20common,and%20severity%20of%20plant%20diseases.

https://pdc.umn.edu/

Trees need at least an inch of water per week, if the soil is dry to 4 inches it needs water. The leaves without the discoloration look healthy and in good shape so your watering schedule looks good.