'Buy Now' vs 'Details' buttons in Featured Products carousel

ZC 1.5.4, Westminster New template.
in Featured Products carousel some products shows 'Buy Now' buttons other shows 'Details' buttons. I can't find any reason for this, no such settings in Admin, Products, Categories, Featured Products. I need all products shows "Details". Here is the testing site http://herbs4cure.com/store/
Any ideas why this happens and how to fix? Thank you for your help.

products with attributes display "details" to show the buyer the product page with all the options, while products without attributes display "buy now" because they have a set price and no options to choose - not sure how to "fix" it...

Thank you.

It's possible in the configuration area to disable the buy now button for products in the product listing. Two controls would need to be modified both under configuration, product listing.
Display Product Add to Cart Button (0=off; 1=on; 2=on with Qty Box per Product) set to 0
And
Display Multiple Products Qty Box Status and Set Button Location also set to 0 for good measure. :)

This will/should push the customer to go down to the product detail in order to add the item(s) to the cart, instead of some from the listing, some from the product page.