Diatom bloom on established tank

[Efaro85]

Our tank is about 4 years old and for the last couple months we have been dealing with Brown algae. Updated my cleaning crew, made sure protein skimmer is working, flow is good, refugium is clear, and water test are showing in a safe range. No new rock added all water comes from two lfs and is RO. Any ideas?

Tank:
60 Gallon tank
20 Gallon Redugium

Fish:
Niger Trigger
Blue Velvet Damsel
Lawnmower Blenny
Engineer Goby
Yellow Watchman Goby

Invertebrates:
Cleaner Shrimp
Pistol Shrimp
Two giant mexican turbo snails
2 Bumble Bee Snails
20 Cerith Snails
10 XLG Cerith Snails
10 Blue Leg Hermit Crabs
10 Red Leg Hermit Crabs
20 Nassarius Snails
2 Scarlet Hermit Crabs

Corals:
Cotton Candy Mushroom
Aquamarine Mushroom
GSP
Radioactive Dragon Eyes Zoa
Alien Eyes Zoa
Candy Apple Zoa

Due in any day:
4 Scarlet Hermit Crabs
10 Red Leg Hermit Crabs
25 Blue Leg Hermit Crabs
10 Turbo Snails
20 Cerith Snails
2 Lettuce Nudis
Blueberry Gorgonian
Purple Sea Whip

Thank you!

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