I would wait about a year till you put the mandarin in. They need a very mature tank with a good population of
pods. The other two should be OK. One word of advice. Ask the
LFS if you can see the lawnmower blennie eat. I`ve seen many a one starve because they would only eat algea and when that ran out they would starve. It`s really a good practice to see every fish eat before you get it.