Is the property manager incompetent or is the market slow?

[Arturo Fuentes]

A commercial property in the Denver area (Littleton) has about 20% of its suites vacant for the last 4 months. When questioned, the property manager stated that the market for small offices (800-2400 sqft) usually slows down during the summer months. Given my minimal experience with commercial properties, I'm not sure if this is true or the property manager is incompetent. Assuming the latter and besides switching PMs, what other actions could be taken, from a landlord perspective, to get these suites leased up? Note that the suites are recently renovated and ready to go. Thanks!