I would lean towards a NO on three dwarf angels in the same tank. Some people have gotten it to work by introducing them all at the same time, but everything I've read and heard say its not recommended. Best of luck if you try it.
Here's what saltwaterfish.com say about angels
Alert - This fish cannot be kept with other Angelfish. If you're attempting to purchase two or more Angelfish for the same aquarium it will cause them to fight and most likely one will not survive, so if you're placing an order that has 2 or more Angelfish in it we will have to place the order on hold until we're able to contact you to ensure you're not putting them into the same tank. If you understand they cannot be kept together, but would like to purchase two or more in the same order(separate tanks, group order, etc.) you will need to write in the Special Instructions area at the end of the shopping cart that you understand they cannot be kept together. Tremendous time and effort is put into ensuring the health of these fish and it is very important that you're fully aware two Angelfish should not be kept in the same tank.
I've got one Potters in my 220 and he is the biggest bully in the tank by far. He beats on anything that is new and close to his size. If i were able to remove him i probably would. So adding another angel would be certain disaster, let alone having three together.