Fix Blurry Instagram Uploads

I have high-resolution photos that look razor-sharp on my computer, but once they arrive on my iPhone via AirDrop and I try to post them to Instagram they lose clarity and appear noticeably soft. I need... (Budget: £10 - £20 GBP, Jobs: Image Analysis, Image Processing, Image Upscaling, Instagram Marketing, iPhone, Mobile App Development, Objective C, Photo Editing, Photoshop)