Your tree's leaves are trifoliate, therefor your tree is either poncirus or a poncirus hybrid. The fruit of poncirus and its hybrids taste horrible. Your original tree must have died and what is actually growing is the root stock. There are many fertilizers much better then E B Stone.

I don't think the entire tree is sprouted rootstock. You need to observe which stems have the trifoliate leaves and eliminate only them. Logically, they would be anything below the graft line, if you are able to identify that.

Is trifoliate the yellow one?

The newer leaves appear yellow on both trifoliate and mandarin.

You've got to go by the leaf form. Rootstocks such as Poncirus, or Poncirus hybrids have a trifoliate leaf. The scion (edible variety) should exhibit a unifoliate leaf. Anything with a unifoliate leaf (no matter how yellow it is) should be saved*.

*This is not always true for rootstocks of most lemons. Some propagators use rough lemon (Citrus × jambhiri Lush.) or sometimes C. macrophylla as a rootstock which also has unifoliate leaves.