Nightfall, and all milestones that give "Powerful Gear" each week. Make sure to equip your highest light level setup before accepting the powerful engrams. I think they are called Luminous Engrams in game.
Also check to see if you have random legendary armor/weapon mods in your inventory from drops. Add those in regardless cause they bump your light +5 each. Once you are at a higher level the next level stuff drops for you with powerful engrams.
Ive mentioned this a few times and no one has interjected. Please correct me if im wrong. But you are lvl 270 and items are still dropping at 266. I was told that the power lvl gained by lengendary mods does NOT count for drops. So if you got to 270 because your stuff has all those +5 mods you kinda need to subtract them to find you true power lvl as far as drops are concerned. It sounds silly but from the nonchalant testing ive done it does seem to be true...but I cant find a source for the info.