looking at your router details it can handle up to 50 clients over wifi, plus it has ethernet connections, so until you have tested the "faulty" devices using ethernet then you havent proved the LAN is ok

if it works on wired ethernet and fails on wifi , then you have a problem , either with the router , local interference , or with the samsung devices themselves

change the cable on the other "wired" tv , also checking it has a valid ip , subnet and gateway

reading the wiki on your device it also mentions that its a dual band router, plus that the N series may not work with other manufacturers devices

so maybe you have the N series and maybe the samsungs cannot work to it ?

or maybe one of your bands has failed and the samsungs use that band ? (but maybe the working devices use the other one ?)

maybe you have set up the apple to wpa2 or some other option and that may exclude the samsungs ?

a myriad of causes may exist, but until you do as I say and check the router admin panel, try pinging the devices from your laptop , try bypassing the wifi using ethernet, then you havent gone through all your options , which is your job to do as the tech support guy for your router and LAN

when its all working , disconnect the internet but leave the apple on, then ping the samsungs, also check the IP , netmask and gateway settings are populated , you will then see I am correct in what I am saying and you may have learned something about "networking" (forget about the public dns settings until the other settings are populated)

think of it this way , to get on a motorway (internet) you have to access it via the access sliproad (local LAN)

if you cannot access the sliproad, you wont get onto the motorway, even if its empty