No suggestions from me. I never had this happen. I hope one of the suggestions above works to get out the red.
Beautiful quilt and quilting.

The table decorations at my daughter's wedding included some silk rose petals scattered on the tables. To my dismay, the sweat from the glasses got on some of the deep red ones and made pink spots on the white cloth table cloths my friend loaned to us. I asked her what she would like me to use on them to try to get them out. She said someone sitting at her table who had seen the pink spots on their table cloth and said Murphy Oil Soap will get anything out of white table cloths. So I first washed the table clothes with just regular detergent so I could see what was stains and what wasn't. While still wet, I treated anything that did not wash out with Murphy Oil Soap, let it lay awhile, until the next load was finished, washed them again. Some stains took several times of reapplying before it came completely out. But I think most of the hard to remove stains were already there when we borrowed them. I am proud to say, they went back to the owner whiter than when she gave them to us. That said...maybe you want to try Murphy Oil Soap.

I would just applique pieces of the background fabric over what has been stained.But find out if it really is from the flowers.Because if it isn't you will have more problems down the road.

Our quilts are a little like Ebola. You can' be too careful.

Be careful of using dish soap. Some of them contain bleach and you may not want that.

I once had a pale peach cotton outfit. I got a coffee stain on it. Someone told me to use dish soap. So I put some on and while I was letting it soak, I told someone on the phone what I was doing. She asked me if I wan't afraid I'd bleach the fabric. Sure enough, now I had white spots on it.

Since it was now white, I decided to bleach the whole outfit and have a white outfit instead of peach. Well, it was sewn with peach poly thread...the fabric all bleached out white but all the threads were showing. So I decided to color it peach with Rit dye.

I put it in the pot and dyed it and it came out an ugly orange. So I put it back in the washing machine with bleach and it came out just perfect.

So just keep trying stuff until you are happy. But, I don't think your quilt is ruined. This quilt is beautiful and I'd use it as is. The spot would make a good conversation piece.

After trying it this way once or twice then try the Murphy's Oil Soap. This is the reason I always prewash just incase this if the fabric bleed. Good luck.

If nothing works, wet the flowers and lay them on the quilt blocks and make a tie-dyed look over whole quilt. Or cut it up and make place mats, totes, etc. Of course these ideas are only if you do not want to replace the block with a new one.

Trying any stain remover on a different piece of fabric that you've stained with the flowers sounds like a good idea. I'd go with synthrapol, or Oxi Clean, as suggested above, or try Goo Gone Stain remover. But again, because of the ivory fabric, I'd try on a separate test piece (similar in color as you don't have any more), just to be sure whatever you use doesn't take the color out totally.

Another option might be the Retro Wash. Check and see if it says it will work. I would also use the Color Catcher to grab the dye that's released and keep it from reattaching to the fabric.

My daughter found a stain remover on Pintrest and I made some and it works like you wouldn't believe! It's 1 part Dawn liquid dish detergent to 2 parts hydrogen peroxide and you can add a splash of water if you want. You shake it to mix it up, and use it like Shout or Oxy and it works. It even removed blood and stains that were a couple of years old. Try it on a scrap and it should take out the stains.