Is it OK for MikroTik RB3011UiAS-RM leds to lit up all at once like this ? (port 4 is unplugged)
They seem to run at once with some interruptions sometimes, instead of staying off and lit up on activity individually.
I found other topics where they said it is a damaged router if it does this.
Or is it because these ports are all under same bridge ? 
They are not perfectly synced - being on the same bridge means there’s absolutely some traffic that will hit all ports simultaneously (e.g. broadcast) along with traffic that wont. Nothing seems amiss to me.
On a LAN, routers often try and be proactive in resolving IPs to Max (Arp Request). An ARP request is a broadcast packet. Your router will query each IP on the LAN for it’s mac address. Devices will also do ARP requests. Windows will try and discover new equipment like TVs and Printers on the network. The more devices you have, the more frequent they blink.
If you’re concerned, you can view your interfaces for how much data is traversing your router. Or use packet sniffer or Torch to get an idea what kind of traffic it is.