So i have downloaded the five "lite" texture upgrades (dungeon, landscape, towns, riften, misc) to my nexus manager and all I have left to do is check the x's. However, every time I check one x for a mod, another one of the five deactivates (changing from a check to an x). How do i make them all download? What is the issue?

This is where knowing how to manually install mods will save you a lot of time. Ive seen people have similar issues with NMM.