Thank you Bela for this fast response!
Sorry for misleading you with the upper information. Actualy, they are all connected to the same switch, but all of them has an interface to the other switches as well (in case of network device failure) It's something like that:
Switch1
/ \
APP1---Switch2---APP2
So all app servers operational interfaces is located on same switch. There is no looped connection in between switches, so it's not a loop issue (I can confirm that by physically check the cables and looking log files from wireshark - no loops there).
Sincerely,
Dani