Advice to Improve Performance Max Campaign Across Different Store Locations?

We’re running Performance Max campaigns for five stores: Telford, Birmingham, Leeds, Manchester, and Crewe. Each store has three asset groups: one generic group and two product-focused groups, using a combination of images, videos, headlines, and descriptions in the assets.

For audience signals, we’ve used:

• Generic terms for the generic asset group and product-specific signals for the focused asset groups.
• GA4 and offline first-party data (e.g., people who booked appointments).
• Custom audiences (competitors and niche-related websites).
• In-market audiences and detailed demographics.

Leeds, Birmingham, and Telford are performing well with this setup, but Manchester and Crewe are underperforming despite having nearly identical setups.

For Manchester, we adjusted by excluding males and older age groups since we primarily target pregnant females. This improved performance slightly, but it’s still significantly behind other locations. For our bidding, we’re using a target ROAS strategy and assigning a store visit value of £50, based on historical data. We've been adjusting ROAS targets to align with current performance and have plans to increase budgets once the issue is resolved.

What else can we do to optimize the campaign for these underperforming stores (especially Manchester)?

Are there specific strategies for fine-tuning Performance Max or handling store-specific challenges that might help?

Side note: Manchester is a new store.