"Normal" QoS, on your leaf switches cannot help as all your traffic is the same (if I understand your topology, on those switches). However, the 2960 switches can easily run out of interface buffer memory, especially if switch has QoS enabled and using the default (or even the AutoQoS) configuration. If QoS is enable on those switches, first try disabling it. If that doesn't work, the (likely) best thing you can to is re-enable QoS, but using a custom QoS configuration that tries to maximize buffer memory for the interfaces. (BTW, with CCTV traffic, the main goal, like for other non-RT video, is to avoid dropping packets.)
For your 3650, assuming there's other traffic sharing links to the FWs besides CCTV (or other ports), then a custom QoS configuration for it might be useful too; one that also tries to preclude any CCTV traffic drops. For starters, if not already configured, you might try configuring "qos queue-softmax-multiplier 1200" global config command. (Further details about 3650/3850 QoS for troubleshooting drops can be found here: 3850 troubleshooting output drops.)
BTW, since your 3650 is a L3 switch, if possible, I would do LAN routing on it and only direct traffic to FWs, when needed. (3650 can also perform basic security using ACLs, likely much, much faster routing and security processing than your FWs, although also, likely, not with all the possible traffic inspection capabilities of FWs.)
