Pictures and other apps not loading

[Parisslk]

I am staying in an apartment with wifi. My iphone 5 connects fine, and the Internet (in safari or chrome) works AOK. But many apps - Instagram, instapaper, strava - won't refresh their feeds, or won't connect to the Internet at all. The Facebook app works, but pictures won't load - and I can't receive pictures in iMessage either. I thought it must be the router, but when I switched on location services for Instagram (it had been off) the problem fixed itself - for an hour. Now it's broken again. The phone works fine on other wifi networks. Any suggestions would be gratefully received. (I have reset settings, turned router on and off, turned wifi on and off, ditto for phone.) Thanks!