When it rains, it pours...LITERALLY!

We've been having a few issues in the downstairs WC but it seemed to be all taken care of 2 weeks ago. This week it's back to slow draining, but it was still working. Even this morning it was still working, but when I came out after cleaning and pouring some more declogger down the toilet and also the sink I saw the HUGE puddle on my utility room floor...So not nice...it's cleaned up now, but this weekend we will have to remove the rainpipe and get in there to see what's going on. At least I saw it and got it cleaned up before Arjan's timba was lost.