Ricordea yuma again arent very tough and not what I would consider a hardy coral at all.
One way to put your best guess forward is to recall how it looked the day you got it. Then compare with what you see now, I know it's hard to do, kinda like trying to watch hair grow, another reason pictures and journals/blogs can be soo helpfull. Helps you see in time lapse what's working and what's not. Assuming it looks exactly like you got it is not a bad sign, in fact if you got it like that and it's still like that means there may be a possibility it's reversing the downward spiral it was headed in.
Ive kept a variety and lost a few to some water quality issues a few months back, nitrates and phosphates and low alk. But the only advice I could pass would be to just be proactive about nitrates and phosphates with some form of deportation whether that be by heavy skimming, refugium, carbon and media, water changes and/or all of the above. Find out where your water quality is at as it may not need moving at all.When you get some more money for a testkit a good one to be your next would be alk and pH test, you wont really need to worry about calcium and magnesium till your tank gets pretty stocked and/or getting lots and lots of coraline growth, otherwise waterchanges will give you everything you need.
In the meantime most of the LFS will test your water for free(especially before buying something as a courtesy) or for a very small nominal fee like a buck. Which if you do before you do another water change it will give you a better idea of how much water you should be changing.
Btw 0-5ppm is perfectly accpetable without any ill effects. Some sensitive creatures
may not thrive in consistant levels of 10+ and some stop eating in excess of 20ppm. Hope that helps
-Justin