D&D 5E - Issues about Reduce/Enlarge

If you are asking Rules as Written, in D&D 5e spells stack unless they have the exact same name. It's int he PHB under Combining Magical Effects, pg 205.

So an Enlarged creature attacking a foe they have a Hunter's Mark on would gain +1d4+1d6 to damage to each attack above what they would normally do.