You didn't fill in your location.
Most locations only have 8 hours of useful sunlight each day, with a lot of that being less than full intensity. 30W x 8h would be 240 Watt hours. The sky must always be absolutely clear, the sun directly against the panel, and the panel must be kept at its rated temperature (probably 25c), so deduct power when the sun heats the panel. If your panel isn't moved to continuously face the sun, deduct some more. If the panel collects dust, deduct more. If you're not within a few degrees of the equator, deduct more for the shorter days in winter.
Your battery will have losses in the charging process. Expect only 80% of the energy back from charging a lead acid. If you are using a 17V solar panel on a 24V battery, you'll need a boost converter to get the 28V that the battery needs to accept energy. If your design is good, it might be 90% efficient.
You need 240 Watt hours each day. At a minimum, you need twice as much panel, maybe 3x.
Your battery is 360 Watt hours, so it will run the fans for about 36 hours. If the solar panel was big enough to keep the battery charged, it would still be dead at the end of two rainy days.