Plugs could be "gas fouled" from all the flooding.
If you have a spare set swap them. A weak spark makes it worse.

If you don't have a spare set or a sand blast plug cleaner, try this.

put all the plugs in a can and pour a little gas in. slosh them around and pour them out on a flat rock. Light a match. when it's done burning wipe the insulator off with a clean rag (careful - hot) and put them back in and start it.