I just bought this Phal which is doing nicely so far in its blooming state. This am i noticed on one of the lower leafs some yellowing...should i be concerned?
Yes but the problem can probably be stopped.
The problem is you have a slight bacterial issue in the area from water being trapped in the junction where the leaf meets the stem.
Pour peroxide in that area to see if you can stop the problem. With luck the yellowing will not progress across the leaf and eventually drop from old age.
I would use the peroxide a couple days in a row.