I don’t use BlogTouch or any other blogging app. Googling for possible answers for your issue (slow loading of photos), I see that this could also have to do with either the file size of the photos or the overall size of your photo library on your iPhone and there are ways to reduce it. But I will leave it at that as I cannot verify anything I’d write.
Just to illustrate the general idea: we often see that people upload photos to this forum with a file size of several megabyte. In reality, for a good quality photo to be viewed on a webpage, a much smaller file size is sufficient, such as 400 kilobyte for example; this speeds up both upload (posting) and download (viewing). In a similar way, the size of the photo library on the iPhone can be reduced without loss of viewing quality because the originals can be kept in iCloud. So perhaps your photo library has grown too large on the iPhone and that is the underlying issue. But it is merely a suspicion that I have and I don’t know how all this is handled by BlogTouch. Apologies if it is too much technical information.