Neither of those plants do well in pots. I would say that the Hydrangea is still young.
Usual reason for non-flowering Peony is being planted too deeply. The buds need cold ripening to for flowers to form.
Neither of them need ericaceous feed. Better with Tomorite for flowers. (High potash).
Black leaves are caused by underwatering, or too much sun, or lack of phosphorus, over watering, over feeding, take your pick.

The peony if only planted in the pot this year will take time to settle. But as Owd say's it may be too deep. Did you plant it at the same depth that it was when you bought it?

The hydrangea is still small. Dont prune it and see if you get flowers next year. they flower on the previous year's wood. so the stems you have now will go onto to produce flowers next year.

But I think the pots are probably going to be too small very soon.

If there are only a few leaves with black blotches then yes remove them. But you are over feeding them and the excess feed will just drain away. they don't need ericaceous feed.