As the DM, a player at my table is playing a Gloom Stalker Ranger, at level 11. This player was able to make an attack on their first turn of combat while utilising two-weapon fighting, per the PHB rules. The player chose to used "Dread Ambusher" on the first attack, missed the second attack granted by extra attack and then used "Stalker's Flurry" as well as their bonus action attack from two weapon fighting. Do these features actually stack like this, or did I make a mistake in allowing this?
When you take the attack action with a light melee weapon that you're holding in one hand. you can use a bonus action to attack with a different light melee weapon that you're holding in the other hand, you don't add your ability modifier to the damage of the bonus attack, unless that modifier is negative.
Beginning at 5th level, you can attack twice, instead of once, whenever you take the Attack action on your turn.
At the start of your first turn of each combat, your walking speed increases by 10 feet, which lasts until the end of that turn. If you take the Attack action on that turn, you can make one additional weapon attack as part of that action. If that attack hits, the target takes an extra 1d8 damage of the weapon's damage type.