That is chelated iron. It's good for the hibiscus and all our little ones are treated with it after they are potted up for the first time. At that stage they are deficient in most needed nutrients and are treated to iron and everything else they need but it is the iron that you can see in the red water. Some pots have been watered enough that you no longer see the red while others still have plenty of iron left in the potting mix. Some get an extra dose of iron later on, too. It is the best absorbed iron that we describe on this page:
http://www.hiddenvalleynaturearts.com/acatalog/minerals.htmCharlie