Treat or not to treat is and has been the subject of many heated threads. Ultimately it is up to the individual. I would recommend looking into the tank transfer method to treat for ich or the possibility of ich.
In the future you can save yourself some headache by not adding fish to a QT in progress. While not ideal the 10g will work in a pinch given they are not very big. I would look into finding a 30g for QT. If you do decide to do tank transfer you can use the 10g for one of transfer tanks. good luck.