Welcome to FishLore!
Is the 55 gallon a 5 year old set up? You should definitely be cycled unless something sent you into a mini cycle. Do you know what your water parameters are. I don't know what your
water change schedule is but that's the first step to solving most problems. If you don't test your water or are using test strips you should consider investing in an
API master
test kit.
As far as the cories are concerned, that's kinda how they act. I have peppered cories. I've had them a year and a half and I don't see them active to much at all. Now that you mention it they do look like they are leaning a little to the side lol. I always used to think there was something wrong but that's just normal for them.