Good spot for some. The riccia does look a bit ragged. If it makes you feel better about the diatoms...my buddies tank is about the same age as yours and going through the same thing. Lots of filamentous diatoms. I helped him clean it out thoroughly last week. We cleaned the filter which was pretty clogged up with the gunk. He has more slow growers, so yours should emerge from it before his. Has the glosso started sending runners along the substrate yet? If it grows vertically you need more light ot make it run. This is how it goes sometimes, adjust based upon your observations with your plants.