Hi Andy, chlorosis is common for Hydrangea or at least where I'm from and it shows decreased amount of chlorophyll which is caused by luck of iron in the soil. What we usually do is to add " green stone" = iron chelate for increasing the level of iron. The same effect would have any iron pins, nails that will rust, splashed around the roots like a kind of mulch. Also, you can change the color of your plants by adding or subtracting aluminum. You are lucky, the weevils are not your Hydrangeas' problem. I can not get rid of mine in an eco way and they destroy my fuchsia. Hope this helps, Antoaneta
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