me wrote:

Hi,

I live in Southeast PA. [...]. I would like suggestions for a tree
species to replace them with. My soil has high clay content and my zone
is 6b. I think the soil is slightly acidic, but I need to retest it.

An ideal tree would be something very hardy that grows fast.

You might consider red maple. I mean Acer rubrum, NOT the
Japanese maple, Acer palmatum, which is sometimes called "red
maple" in error.

It grows in your area, has good fall color, is relatively fast
growing, and is relatively sturdy. It is hardy (able to
withstand cold) up into zone 3.

Mike
On the North Carolina coast - Zone 8a
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