Looks like two or three things went wrong. First, the large casting on the left should have been attached by a large sprue at the base of the shank of the ring centered over the main feeder sprue straight up. The heaviest castings should always have the center, top most position. I like to attach side feeder sprues to things that look like they could use the help.
It looks like your flask may have cooled off too much before you cast. Try utilizing an assistant; you melt the metal in the crucible and then when it is molten, get the assistant to put the flask in position straight from the kiln. Or, do what I do; take it out as soon as the temp goes down to about 1100 degrees and let it cool down in the casting unit a little while you are melting your metal.
If you are melting your metal with a torch, you should make sure it is thoroughly melted before casting. You should be stirring it with a heated graphite rod to make sure that everything is molten. And, this is the most important thing, even when it is molten, often it is not quite hot enough to cast. You need to see a " ring of fire" around the molten mercury-like metal first. Then, the second most important thing, you remove the torch and release the caster simultaneously. I have a problem with this myself, so I lift the torch on the count of "one" and release the caster on "two". I'm always afraid that the caster will hit the torch and this is my solution. Make sure you are using some borax flux, too, as this makes the metal more fluid.
If you are doing a vacuum casting, the sprues and temp of metal can still be the problem. The orientation of the sprues are different for centrifigal casting which should be like a "Y" and vacuum casting, which should be like a "T". I'm too lazy to explain why, but if you think about it, it makes sense. I didn't think about it and had an absolutely heartbreaking failure with five hand-carved complicated wax carvings that looked a lot like your casting when I did my first vacuum casting.
My side sprues are always much thinner than my central feeder sprue, otherwise the clean up is too difficult.
Sorry if you know most of this already, if you do, maybe it will be useful for someone else in the future.
So, position of the sprue on the piece, finest area to heaviest area, in other words, on a ring put the main sprue on the shank. Position of sprue in the flask; heaviest in the middle topmost. Thorough heating of the metal in a hot-enough flask with flux. Finally, releasing the caster at the same time as you raise your torch.
All of that said, it looks to me that your metal or your flask aren't hot enough, maybe both.
P.S. It also appears that you are doing a flask that may be larger than you can get away with for a 5 hour burnout. Remember, when you look at the charts what really matters is the width of the flask, not the height. Again, think about it and it makes sense. The heat is coming from the outside of the flask going in to center, and if your flask is wide it takes longer to come to temp.
Hope this helps.
Debbie K