Very slow when more than one full-text in query

[James H]

This query takes 0.03 seconds:
RESET QUERY CACHE;
SELECT * FROM (fw_items fwi, fw_departments fwd, fw_aisles fwc) WHERE
(
MATCH(fwi.brand_name, fwi.product_name_and_size) AGAINST(+'BEER' IN BOOLEAN MODE)
)
AND fwi.department_id = fwd.id and fwi.category_id = fwc.id and fwc.department = fwd.id ;

This query takes 0.14 seconds:
RESET QUERY CACHE;
SELECT * FROM (fw_items fwi, fw_departments fwd, fw_aisles fwc) WHERE
(
MATCH(fwc.name) AGAINST(+'BEER' IN BOOLEAN MODE)
)
AND fwi.department_id = fwd.id and fwi.category_id = fwc.id and fwc.department = fwd.id ;

But this query takes 1.22 seconds:
RESET QUERY CACHE;
SELECT * FROM (fw_items fwi, fw_departments fwd, fw_aisles fwc) WHERE
(
MATCH(fwi.brand_name, fwi.product_name_and_size) AGAINST(+'BEER' IN BOOLEAN MODE)
or
MATCH(fwc.name) AGAINST(+'BEER' IN BOOLEAN MODE)
)
AND fwi.department_id = fwd.id and fwi.category_id = fwc.id and fwc.department = fwd.id ;
...but I'd have expected it to take abour 0.03 + 0.14 seconds.

Is this a problem with using multiple full-text searches in one query, or is it something more general? Any idea on how I can make the third query quicker?

Thanks,
James