It looks like it is a salt build up possibly from
nutrients or the water you are using. Does the hydroton also have the white build up? If this persists it will damage and kill the plants. Buy Clearex it will help clear it up but you have to find out whats causing it.
Don't use full strength nutrients use only 1/4 or 1/2 strength. If you are still getting the salt build up then you need to look at the water. I know the water down in Florida is not very good. Not sure if you can find out what is in the tap water even though you are using a filter. If you can set up something outside to capture rain water and use that instead.