re: What is the maximum size for the pictures?
Depends on your web host. The max size I recommend is not much larger than the size that you are displaying.
re: They had always been their current size and started causing problems earlier in the year.
The absolute max size depends on the memory allocated to php by your web host. Generally a web host will allow you to set it to 128MB, many will even allow up to 256MB. Now, you can actually set PHP to any amount of memory but it will be silently “hard” limited by the webhost.
Why all this talk about memory?
Processing images require memory. Opening an image for processing can take 4 or more times the memory that the image file size. So processing a typical image that comes any modern day cell phone can easily exhaust the memory allocated to PHP.
Now, this memory needed to process an image, that is also shared by WordPress and all the other plugins that are installed on your site.
This leads me in why now…
This could be due to many factors.
- The webhost made server side changes that you would not be aware of.
- WordPress, plugins and theme are all needing more and more memory.
- Sometime in the last year, just one image was uploaded that was too large and it is just that one image that is causing the problem.
It could be any or or a combination of all or more or even none of the above and the reason is another that I can not think of at the moment.
Honestly, I think it is that last one. I see you have a max upload size set to 64MB. If you or another user uploaded a multi megapixel image that could easily cause the problem.
Hope that helps!