|Well, upon rereading your original post more closely I would again suggest you get UPS's fast.|
Also, stop daisychaining switches wherever possible. If your router has 4 LAN ports and you only have 3 switches then all switches should be plugged into the router directly, not into another switch. The reason you don't want to daisychain is that the bandwidth aggregates. So the switch connected to the router that has another daisychained to it is carrying the full bandwidth of both switches. This can cause issues with throughput.
I'm thinking perhaps some, if not all, of your wireless clients were on and running when the power went out. If so, then the issue could also be with their wireless network interfaces. I would recommend updating the drivers on all of them that aren't already using the most recent drivers available.
Also, you may have to update or replace your AP's. They could have been adversely affected by the power outage too.
Wireless is inherently susceptible to lag and latency and even though you have a strong signal and a solid connection, it will still never perform as well as an equivalent wired solution. Keep in mind too, you're only getting 54 Mbps with your present wireless solution. Wired clients are getting no less than 100 Mbps and more likely 1000 Mbps.
Are your wired clients having issues too or is it only the wireless ones? If it's just the wireless ones, well, that tells you a lot right. Wherever possible, and wherever it really matters, clients should be wired, not wireless.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.