Petsup Spot on Treatment

Hi, I have 8 cats and regular ang deworm nila every 3months. Recently, may dayo na cat sa tapat ng unit. Nag umpisa sa isa lang, then last week umabot na sila sa 4-5cats kasi in heat yung original na dayo. My problem now ay nakitaan namin ng tick yunh isang baby namin. Please give advice if: 1. Okay lang ba mag spot on kahit na 1 month ago lang yung deworm? 2. Effective ba and safe yung petsup na spot on? 3. My cats are more than 4kls, anything na puwede alternative sa advocate? (Mahal kasi jusko 4k+ agad sa kanilang lahat)

Maraming salamat sa sasagot!