Question
should i fertilize azelias and if so, when ( after they bllom, before etc)

Answer
If the azaleas are planted in good organic soil and are not showing signs of problems, then it is not necerssary to fertilize yearly. A 1/2" covering of leaf mold or compost in spring or fall is recommended.

You can fertilize, and I recommend doing so in spring just as the flower buds have formed, or just at/after flowering.

I prefer to use Holy tone (by Espoma) which is a very good organic alternative. The reason I like this is that it feeds more when soil warms and less when soil is cold thus matching the uptake by the plants excellently.