General Network troubleshooting

I own a small business with Microsoft HyperV with 6 virtual server running Windows Server 2008r2, SQL Server 2005, Exchange 2007, etc on a network of about 15 computers, various networked printers, ASUS wireless router, wireless access point etc. Lately it's been acting strange, can't ping existing devices or it returns ip6 id's vs ip4 even though devices are listed on the network in the ASUS RT-AC3100 router. I've tried troubleshooting as much as I know how including rebooting the servers, router, switches and PC's. It seems to be getting worse, now my Outlook 10 won't connect to Exchange 2007 where before it was working fine. I can connect just fine with OWA thru a browser though. I'm hoping to find someone who is knowledgeable with networking, routing, DNS and other things who can help me find the problem and figure out how to fix it. I'm fairly technical and have been working with computers and networks ever since Netware ELS II and coax cables, I have a lot of experience but I'm not a professional, I'm a generalist and can pretty much get things done when I need it at least most of the time... I did have a professional computer consultant setup our servers a few years ago, I know I need to update to latest software but haven't had the time or money to buy new hardware and software and what we have has been working just fine up until about 2 weeks ago when things seemed to start acting up. If you are good at logical problem solving and have the experience and knowledge of the type of equipment, software and environment we have, I would love to get a couple hours of your time and have you take a look at things, then if you decide you can help and need more time to fix it we can talk about it. While you are at it, I need to get my backups working again too, I have a couple of iSCSI NAS and a backup server running microsoft backup that was put in place when we got our hyperv but the backups stopped working and I haven't had time to figure that out either... Can you help?