Not sure if I should take them to the vet

Question
I recently got a young male rat from the pet store (not the best place, I know). He was sneezing a little, but that was it so I figured it was only environment change sneezes. I put him in with my other two males since he seemed very healthy otherwise. A week later and my older bucks are also sneezing (they sneezed in the first place because I live in a basement where there are some allergens, but it intensified). They have a bit of discharge, but only out of one eye. They still eat and play and I don't think they've become lethargic, but they have a kind of congested sound when breathing occasionally. It doesn't sound like it's coming from their lungs, just their nose.
I've been giving them collodial silver in the hopes that it helps them. As for right now, I'm not sure if they're sick and if I should spend lots of money to take them to a vet. It occurred to me that they may also be reacting to the environment change of having the young one around, but I'm not sure seeing as this is the first time I've owned rats.
I'd love some advice from someone who knows more. Thank you for reading this.

Answer
Hi Drea, first off, I offer apologies for the delay in responding to you.   Chances are that all have respiratory infections that the new boy brought in.  My recommendation is to treat them all with Baytril.  You can either take them all in to the vet to have them weighed and have the vet prescribe appropriate dosages of Baytril based on their weight, or you can order Baytril online, assuming that you have an accurate scale to weigh them, that you have a syringe to measure the Baytril, and that their illness is still manageable and you can wait the several days to receive the order.

If you choose the latter, you can order Baytril (also known as Enrofloxyn) from this website:   http://www.ladygouldianfinch.com/product_baytril.php
This is where i purchase my Baytril as well as many other rat owners.  The dosing information is based on each rat's weight, as indicated below:

Baytril Dosing Information
10% ENROFLOXACIN LIQUID (BAYTRIL)
All Forms of Baytril are dosed at TWICE per day and calculated at 15mg/kg for respiratory disease.

DIRECTIONS FOR GIVING IT UNDILUTED, AS IT COMES IN THE BOTTLE.

Squirt this tiny amount of Baytril 10% Liquid into one serving of a food treat. Do not use acidic foods like fruit juice or baby food peaches. Stick with non acidic foods like cake, baby food beef or turkey, etc. Pudding is fine too.
DO NOT REFRIGERATE
DO NOT SQUIRT UNDILUTED DIRECTLY INTO THE RATS MOUTH

Rat weight     ml undiluted
700 gm         0.10 ml
600 gm         0.09 ml
500 gm         0.07 ml
400 gm         0.06 ml
300 gm         0.04 ml
200 gm         0.03 ml

i hope this helps and your boys reecover quickly.  Please contact me again if I can answer any other questions.