Do yourself a favor and fix the back blade before it breaks. Weld a piece of thick 2" (up to 3") angle iron from center to edge. If you can get some 6" C channel in 3/8" thickness that would be better. The center of the extra material should be about 1/3 up from the bottom for the angle iron and a bit further up for the C. The rear blade you have there is VERY light duty, your tractor will eventually bend it up pretty bad. It's much easier to weld on extra beef to a straight blade than to try and straighten it and add be beef later.
You should also see about beefing up the box blade and adding weight to it. I would guess that your BB is about 550 pounds. Way too light to dig effectively. For example, my BB is 5 1/2 ft wide, is around 950 pounds and is still too light in hard pack clay soils. Add some 3/8 or thicker plate steel on the ends (inside and out), weld extra angle iron pieces to the scarifier holder bar and add some structure behind the blades to keep them from bending. If you snag a large rock in the center of the blade, it will pretzel the box pretty dern quick.
On the rake, I would extend the center square tube end to end to keep from twisting it up.
Sounds like a lot of busy work, but adding beef now will allow the tools to last a lot longer.
It's also a good excuse to buy a welder.....
jb