With the Swiss Pass, are there any additional fees to take the bus/train from Lugano to St. Moritz, train from St. Moritz to Chur, & train from Chur to Zurich Airport?

I am planning to take te bus from Bernina express bus from Lugano to Tirano, then the Bernina express scenic train from Tirano to St Moritz on the same day and have already made the seat reservations by e-mail for $12 CHF/person for the bus and the train(total seat res cost of 48CHF for 2 people). I haven't purchased the tickets yet for that or for the train I will need 2 days later to Chur, and another train I will take from Chur to Ziruch airport the following day. With the fall 2-for-1 promotion for the 4 consecutive day swiss rail pass for $242 for 2nd class, it seems as though I'd be better off buying the pass than the 3 individual tickets. However, I want to make sure that other than the seat reservations that I've already made, I won't have to pay any other ticketing fees to take the bus/train Lugano to St Moritz then 2 other trains(St moritz to Chur and Chur to Zurich airport, all within a 4 day period. Can I get assurances that I will be able to do what I intend to with the 2-for-1 passes for only $242. Thank you
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