It's common, a cycling tank is very unstable and you'll see a lot of algae growth during this period.
A note on cleaner magnets: You need to remove the inside magnet (scraper portion) and rinse off the algae you scrape when you're done. Otherwise you aren't really cleaning it, you're just moving it out of the way for a few days until it spreads back out into the tank. Don't scrub off felt-like scrubbers when cleaning them, just let the water fall onto it and dislodge it with force.
"The only thing that happens fast in saltwater tanks is failure."