Hi Lloyd - Yes as Colu said, Rams generally like to be warmer. If it was Pets at Home who gave you the advice I'd always take it with a pinch of salt - When I first started out my only local fish store was Pets at Home and I listened to them and lost a lost of fish. Since then I always try to find a small outfit / family run place, if I can; in my experience they tend to care more, and so be a bit more knowledgable, generally.
So in my opinion, Rams need to be warmer than that (i.e. 26 C or higher), and that is probably a bit reason why you lost them unfortunately. As Colu said, maybe some cold water fish might be better options (danios, white clouds, or some types of platy, such as variatus, as well). I agree your Ammonia is probably too high as well, but Nitrates are a little more flexible in my opinion. I would recommend testing your tap water to see what the Nitrates come out at, because if you change loads of water but your tap is already at 25ppm, it won't make any difference. A natural remedy of sorts to nitrates is to add plants to your tank - As they grow they will eat up the nitrates (and any ammonia) as fertilizer, so if you don't have any plants at the moment that might be a good option to help out. You also don't necessarily need planted substrate or anything - Plants will readily grow in normal substrate, eating up fish poop, etc, but make sure the substrate is porous enough for their roots to grow (i.e. very fine sand is usually a no go, but everything else should be ok).
Hope this helps!