Photo? Difficult to diagnose without being able to look at it. I wouldn't worry about the lack of flowers since it was only planted last year. The leaves might indicate a problem. do you know what your soil pH is? Did you amend only the planting hole? If so, try sticking your finger down into the soil a few inches next to the plant. How soggy does it feel? Sometimes amending a planting hole only when you have clay soil will cause water to collect in the hole, sort of like a bathtub.

My soil is alkaline and I tend to observe this yellowing trend too when we have a lot of rain. I then add iron-chelated liquid compunds, sulfur or aluminum sulfate to change the leaves. Mind you, the yellowing will dissipate slowly on its own if I do nothing but who wants the dark green leaves staying yellowish for a long time. ;0) Ha!

the area is pretty widely amended and I'm a very seasoned gardener BTW so I've prepped the space well with my usual mix for this area and have been successful in previous homes (in the same general area). Northern ontario has a largely clay soil left behind during the glacial age. So, we have clay in our area, ph is neutral although I haven't done much testing. My surrounding plants are thriving. That includes bleeding hearts, delphiniums, hostas, astilbes, butterfly bush, goat's beard (I think), greek oregano tiarellas and coral bells. Nearby I have a vegetable bed filled with tomatoes and zucchinis. I'll see if I can do a closeup and post it. but the more I look into the leaves and see that green veining, the more I think its a iron deficiency and perhaps that is the problem. Its been incredibly rainy this summer and I mean moonsoon type rainy. The plant itself is okay and producing more leaves. just a yellowish.

I prefer using organic ways to amend soil and will check on other means to increase iron.

Ability of plants to access iron is directly related to soil pH - acidic soils tend to make iron available; neutral to alkaline soils restrict access.

btw, chelated iron products, sulfur and aluminum sulfate are all naturally occurring materials so they are considered "organic" amendments.

The first step is to test your soil's pH. Hydrangeas prefer an acidic soil so it should test out somewhere in the 5.0 to 6.5 range.