It's not uncommon for this symptom of collapsed and dead/brown leaves to appear around clumps of Lamb's-ear, but the exact cause can be hard to determine. Typical culprits include fungal issues like Southern Blight or some other type of stem or crown rot (there are several species of fungi in that group). All of those diseases are favored by humid, stagnant air or damp conditions (whether from weather or over-watering), which is typical of the dense growth of certain groundcovers. If you happen to irrigate this garden bed, make sure the soil is getting fairly dry a few inches deep next to the Lamb's-ear before watering, as it has good drought tolerance and does not want to stay damp. Leaves that remain wet for long periods, or which are wet-down frequently, can be more vulnerable to infection by disease spores.

Brown or yellowed leaves will not recover, so you can remove and dispose of them (don't compost). With improved air circulation around the base of the plant once they're gone, the plant might stabilize and not develop more dieback, but it's not practical to use a fungicide for this situation, nor would one be able to cure any existing infections (they only work preventatively to protect healthy growth).

Miri