You're readings are pretty good, but there shouldn't be any nitrites. I would test every day until they get to zero. If they go over 0.25ppm then do a water change.
I think a lot of people do water changes at least every two weeks, regardless of nitrates. It's a good habit to get into.
A. Lilicina is one of the easiest red plants to keep, but they still need a little more light than what you have to keep algae away, from my experience. The second plant should be pretty good. I've never had it but I've heard they do well in low light. I would stop with the plantamin because it's not really needed and it's more likely to cause algae. If you want some kind of fertilizer, try root tabs. I would wait at least two weeks after ammonia and nitrite are zero for cories because they are delicate fish.
OK cheers. Will test each day to see what it is. I've ordered some java moss aswell now, gonna try and get some slate for it to sit on.
Really like your marine tank by the way, been reading your journal
By the way is mg/litre the same as ppm??
cheers
Dave