ALWAYS use sunscreen if you have any tats that the sun can touch. humm... but i've never heard of them doing that in the heat/humidity. I've heard of them bubbling from bad ink or skin cancer. i'd check with a certified tattoo person just to make sure.
you know how old guys with tattoos from old wars and shit have crappy tattoos that are all blurry... well, that's what happens when they go too deep in the skin. you need a new tattoo artist 'cos in a few years your work will start getting blurry and seeping into your skin.
taking care of them and having a good artist doesn't really matter when your dealing with how deep they are in the skin. the bottom layers of skin are not as "tough" as the upper layers and that's what makes the inks run and make the work look blurry.