Invisalign large black triangles, food traps, and gum recession (Photo)

At your age, the tissues may fill in when treatment is complete, but not always.  This is not a sign of ANY damage.  This is due to crooked teeth not allowing bone to be between the teeth, and when properly aligned, no bone is there.  If braces are done at a young enough age, the bone is still developing (which is why black triangles are rarely a side effect of orthodontics to teenagers).If the tissues never fill in, consider Bioclear.

As you clearly stated, you already had periodontal issues, and gum recession before treatment began. You also state that you are just a little past halfway done with your programmed aligner schedule. You cannot be concerned about where teeth are currently. They will continue to move and change. Ask your provider to show you the clinchek that was don on your mouth. I would assume you will find a similar look at this stage of your treatment. 
If you continue with proper hygiene and normal dental cleaning visits, invisalign will NOT cause damage to your gums. In many cases, after completion of treatment and teeth are no longer being moved, the gum will mature and MAY reduce some of the black triangles. 
Show us some photos of your teeth before any treatment started to assess the amount of recession originally.