Home printer printing dark photos but when I buy online they look fine?

I bought a new photo printer its a canon m7720. I didn't just buy it for photos I needed it for school since I'm homeschooling an thought I could get the best of both worlds. I took some photos on my phone when I went to the zoo and got them developed online from mpix and the pictures looked great just like they did on my phone no difference. Well I took some pictures with my camera and went to lightroom on laptop bc they needed to be brightened up an then after wards I transported them to my phone bc I havnt quite figured out how to print from lightroom with out leaving a border around my picture. So I put the picture on my phone then went to my lightroom app just to soften it up a little more and the picture looked great. I just wanted to print a simple 4x6 picture for my friend since it was of her daughter, but when the picture came out of my printer it looked nothing like it did on my phone. The photo was extremely dark. Why was it when I printed my phones pictures online come out looking just like it did on my phone but the picture I printed from my home printer from my phone come out extremely dark? When I transported the photo from my laptop to my phone and then took it to my app to mess with it, it changed the photo as if it was from my phone so I don't think bc one came from my camera to laptop to phone made any difference since both photos were in the same format. The only difference was one was printed online and the other was printed on my home printer.