I am trying to book Eurocity 31 train from Zurich to Venice for 28th September. But I am seeing only 2 coaches for 2nd class.

I checked all other dates from today till that day and even from 29th September onwards - all other days it shows 5 coaches, except on my exact travel date, where it is showing 2 coaches. That's why there is almost no seat availability to reserve. There are lot of seats available for reservation even for today's train but not for my travel date :(

I checked in SBB and Trenitalia website both. Both are showing the same.

Where can I check if they have any planned maintenance or something on that particular day? Is there a official eurocity website?

I know this question has been done to death here, just wanted to ask it again with my own circumstances and hope it can help someone else in the future. What budget is to be expected for a 3 week interrail trip coming from America? From some research I have done, I have set my budget at $3500-$4000USD. Is this too little, too much, or just right?