Leslie, I do not believe your photo posting tool--iPhone or "better camera" is not the problem with picture photo quality displayed on this forum. It is the technology you are using. I have had similar problems and I use similar technology as you do. I use an iPad and Tapatalk. This all started when iOS was updated on Apple devices this past Fall.
Pilot and Jayfar recommended I use a photo hosting website like Flickr to upload my images and from there copying the HTML/BBcode data file of a particular photo and pasting it here. It sounds difficult, but once you do it a couple of times it gets easier. You also use Facebook to post pictures. I do not, so I am unable to advise you in where to get the HTML/BBcode in Facebook, but I'm sure that is available. The nice thing about this method of posting photos, is you have to deal with the photo once but you can attach and post the photo to many places.
Tapatalk
Flickr
Hagoromo 羽衣 by
MattWoelfsen, on Flickr
You also have the ability to post more than one file without diminishing subsequent photos.
Tapatalk
Flickr
Amami-Tensen 奄美天泉 by
MattWoelfsen, on Flickr