Apps 6tag and Whatsapp often won't open, why?

[SLoy87]

Apps 6tag and whatsapp often won't open

Hi all,

Since only recently I am having an issue with my Nokia Lumia 930.
Often I just cannot open whatsapp or 6tag. I can select the apps as much as I want but it doesn't open or it opens and it takes a long while to load and then finally hangs up.

I cannot link this behavior to any recent changes. My phone is already on wp8.1 for long time.

Actions so far:
- Soft reset phone
- De-install and install apps

Is it possible that my phone has a virus?
Could you advice on any actions?

Regards,
Steven