Nathaniel Davis i'm afraid they may have because the actress who plays immunique has landed on another sitcom. but don't worry i still have quite a few more eps. to upload.
Tatyana Ali wasn't really replaced. Being that she played the role of the daughter. Reagan Gomez is playing the niece. Basically they kind of wrote Tatiana off the show
This is a normal aspect of tv series' always has been and always will be when the actor gets written out of the show either temporarily or permanently for whatever behind the scenes reason I don't know why Tatyana seems to have gotten written off the show maybe she took another role with another show...WHO knows there could be any number of reasons why but it is a normal expected aspect of almost any tv series that runs long enough that there will be either some temporary or permeate write off along the way when dealing with real human beings and thier real human lives behind the scenes of the show. Research almost ANY tv series of the past and present that has ever ran for long enough and you will likely find write offs of characters because of real life real human being behind the scenes reasons. Sometimes in the actor's favor (a better opportunity with another role elsewhere) and sometimes for a numerous amount of bad reasons.