Please help!!!
Thanks for the info, I forgot one last thing to ask what your temperature is!
The pH is a touch on the high side for those South American fish but still reasonable. I think your fish will be happier if you lower it more towards 6.0-6.5 but that's probably not the cause of the ram's problem.
The large water change might have stressed out the fish enough to make it susceptible to an infection or something carried over from the turtle tank. Turtles are dirty things and the bacteria might have invaded the fish tank, just needing the right time to make a fish sick when it got stressed and it's immune system was compromised. If that was the case, you might as well try treating the whole tank for bacteria. No point in quarantining the ram and getting it healthy again, only to stick it back in an infected tank.
The driftwood tannins are actually very beneficial for fish like rams and angels and are part of their natural habitat. The only reason to remove them would be for aesthetic reasons. While I'm sure the driftwood has become a home for lots of good bacteria, it would be better for you to just take it out and boil the wood or let it soak in its own container so you don't cause a big disruption like that to the tank. Big water changes are hard on your plants and can stress your fish. You cause more harm than good by making such a huge change for purely cosmetic reasons. Big water changes always come with risks and negative consequences for the tank, they should really only be done when the benefit outweighs the drawbacks (and with planted tanks, you have extra drawbacks to consider.) Supplementing with plant fertilizers alone won't replace the natural balance between fish waste and plant usage. Treat the wood separately, then put it back in your tank.
That said, I personally highly recommend leaving the tannins in your tank, if not supplementing more by adding almond leaves or magnolia leaves. It looks weird at first, but you get used to it and fish like that love it! There are some videos on YouTube of people who filmed the natural habitats of South American fish like the rams and angels and they came away saying one of the mistakes made in the hobby is trying to keep fish like that in pristine, crystal clear tanks. The tannins, leaf debris, driftwood, all of that is what those fish are used to and thrive in, not a pretty tank fully of crystal clear water. Those fish come from tropical forest rivers that have all sorts of stuff falling in. Clean is totally alien for them.
If you just can't stand the look of the tannins, treat the driftwood outside of the tank (boil, soak in a container) or replace it with fake driftwood. PetSmart has a variety of fake driftwood pieces, some of which are quite large and would work in a 55 gallon. They look pretty realistic and would obviously be tannin-free.
If you do remove the real driftwood (and as you remove tannins,) you'll need to closely monitor the pH. The tannins lower pH and help create a natural buffer, but once you lose that you don't have much room for your pH to raise before your fish and plants will suffer for it. Plus quick swings in pH are very bad for the tank ecosystem, even if the pH remains within the "safe" range for the tank inhabitants. Slow changes are safe changes, fast changes are deadly.
A great website for pro-tannin tanks is Tannin Aquatics (
www.tanninaquatics.com) which has a good variety of products for promoting tannins in addition to the ubiquitous almond leaves.