I'm seeing some yellowing (nothing major at all) on my crypto parva and some on the edges of my lutea.. Now I'm wondering if maybe this is due to lack of Fe? Also, some of my tropical hornwort is yellowing but most stays a very nice hue of green. I'm just not seeing that vibrant green on the crypts, is this just normal for a low tech tank? 1.2 wpg, neutral/soft water..