You just have to square them up to be the same size as the black. Use a ruler just about the same size as the size block you want; like a 6 1/2 or or whatever. Then find the center of the block and for a 6 1/2 in block the center of the ruler is 3 1/4 and that should be in the center of block on all 4 sides and then trim each block so that they are all the same size. You might consider a white or another color for sashing and then you don't have to but up seams or alternate the blocks on each row so that the black buts up with the pink and white each time and then you don't have to worry so much about matching seams. My daughter made a block quilt and the blocks were off but I didn't want her to get disappointed and quit quilting so I made sashing to put between the rows of blocks and then it didn't show as much that the blocks weren't 100% the same size. I even had to take one whole row apart because there was way too much off in size but I didn't tell her, I just put it all together and then taught her how to do some SITD and tied it off and she gave it as a baby gift and the new mom and all the guest thought she did a great job. She told me later, how can they say that I made so many mistakes. I told her that only someone that quilted or knew to look really careful would see them. Most people look at the gifts; not the mistakes. Her next quilt was so much better and she did it all by herself. I was very proud. I think you are on a role here and can have a very pretty quilt if you keep going.