Novice, if your soil is alkaline, your hydrangea is going to bloom PINK! You can add something to the soil to make it more acidic (causing BLUE flowers) but so far, I am in the mid-south area and I've always had blue flowers on my hydrangeas that I plant outside. It's possible a rabbit is nibbling at the hydrangea leaves if it's only down low. When my hydrangeas start to bloom, the buds are a cream color. As they open the blue color fills in. So that may be why your buds are rust color (going to be pink when fully open) Good luck. Maybe the link below will help you out! Here is a link that might be useful: About hydrangeas

I have a Tardiva in my garden, but I don't think this plant is a Tardiva. The blooms on my Tardiva are more airy and bloom later than the plants where I took the cutting. The blooms on my Tardiva have no smell at all. And like you, I had never noticed any smell in hydrangea blooms before either. But this particular bloom definitely had a smell to it. I need to go back to the original plants and "smell" some of the blooms on the plants. Perhaps the bloom I had was just "a bad apple" so to speak. LOL Thanks!

Definitely not Acer griseum - that too would have long oval and entire cotyledons present at this stage and an opposite leaf arrangement. Also Acer griseum is notorious for producing a high percentage of nonviable, sterile seed - it is estimated that only 1-8% of any seed produced will germinate so chances of a spontaneous paperbark maple seedling is remote at best!!

Check undersides of leaves for little white larvae that look like grains of rice and/or fluffy white cocoons. Or a sticky clear residue on tops of leaves. If so, it is most likely whitefly, which I am currently battling myself. I have a pachira money tree, a similar looking plant to yours, with very similar recent leaf damage. they are resistant to most pesticides so neem oil is one of the few “pesticides” that kill them. But you have to be diligent and thorough with your application-every 7 days, spraying all parts of plant, particularly undersides of leaves. I’ve knocked mine back some w/ 2 treatments already.