It would help an enormous amount if you were to clear that ivy away!! Otherwise, it may just be slightly behind its cousins nearby.

To expect plants to perform up to par, you must provide them the growing conditions that will optimize performance. Having the root zone smothered by a layer of ivy is not achieving that result.

Exactly what I was going to say.

I ended up removing some of the ivy around it. But I also noticed that some branches on the same plant were in full bloom and leafed. So I’m guessing the rest are on its way to death?

Give it one full season of no weeds underneath it, regular water, a topdressing of compost, and mulch.

Re-evaluate it next year after it's had some time to recover.