According to your graph they are, but are all those device down the line from the MikroTik in bridge mode or are there any routers in the mix as well?
Bridging between various brands of network equipment can be tricky business or even not work at all. I would go for routing instead, but you try it out.
Go to each box and try if these get to the internet or not (ping something (8.8.8.
for instance):
Does the Dlink 624 (192.168.0.1) make NAT for the 192.168.0.0/24 network?
Does the Dlink 624 (192.168.0.1) get to the Internet?
Does the Mikrotik AP (192.168.0.30) get to the Internet and/or can it ping 192.168.0.1?
Does the Dlink 2100 AP (192.168.0.50) get to the Internet and/or can it ping 192.168.0.1, 192.168.0.30?
Does the Dlink 2100 AP (192.168.0.51) get to the Internet and/or can it ping 192.168.0.1, 192.168.0.30, 192.168.0.50?
Does any Client PC (192.168.0.100) get to the Internet and/or can it ping 192.168.0.1, 192.168.0.30, 192.168.0.50, 192.168.0.51?
You can try pinging another way around toward the client side as well.
As a result of all that pinging around You'll see what hop is broken.